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<h1><img src="postfix-logo.jpg" width="203" height="98" alt="">Postfix Configuration Parameters </h1>

<hr>

<h2> Postfix main.cf file format </h2>

<p> The Postfix main.cf configuration file specifies a very small
subset of all the parameters that control the operation of the
Postfix mail system. Parameters not explicitly specified are left
at their default values. </p>

<p> The general format of the main.cf file is as follows: </p>

<ul>

<li> <p> Each logical line is in the form "parameter = value".
Whitespace around the "=" is ignored, as is whitespace at the end
of a logical line. </p>

<li> <p> Empty lines and whitespace-only lines are ignored, as are
lines whose first non-whitespace character is a `#'. </p>

<li> <p> A logical line starts with non-whitespace text. A line
that starts with whitespace continues a logical line. </p>

<li> <p> A parameter value may refer to other parameters. </p>

<ul>

<li> <p> The expressions "$name", "${name}" or "$(name)" are
recursively replaced by the value of the named parameter. </p>

<li> <p> The expression "${name?value}" expands to "value" when
"$name" is non-empty. This form is supported with Postfix version
2.2 and later. </p>

<li> <p> The expression "${name:value}" expands to "value" when
"$name" is empty. This form is supported with Postfix version 2.2
and later.  </p>

<li> <p> Specify "$$" to produce a single "$" character. </p>

</ul>

<li> <p> When the same parameter is defined multiple times, only
the last instance is remembered. </p>

<li> <p> Otherwise, the order of main.cf parameter definitions does
not matter. </p>

</ul>

<p> The remainder of this document is a description of all Postfix
configuration parameters. Default values are shown after the
parameter name in parentheses, and can be looked up with the
"<b>postconf -d</b>" command. </p>

<p> Note: this is not an invitation to make changes to Postfix
configuration parameters. Unnecessary changes are likely to impair
the operation of the mail system.  </p>

<dl>
<DT><b><a name="2bounce_notice_recipient">2bounce_notice_recipient</a>
(default: postmaster)</b></DT><DD>

<p> The recipient of undeliverable mail that cannot be returned to
the sender.  This feature is enabled with the <a href="postconf.5.html#notify_classes">notify_classes</a>
parameter.  </p>


</DD>

<DT><b><a name="access_map_reject_code">access_map_reject_code</a>
(default: 554)</b></DT><DD>

<p>
The numerical Postfix SMTP server response code when a client
is rejected by an <a href="access.5.html">access(5)</a> map restriction.
</p>

<p>
Do not change this unless you have a complete understanding of <a href="http://tools.ietf.org/html/rfc821">RFC 821</a>.
</p>


</DD>

<DT><b><a name="address_verify_default_transport">address_verify_default_transport</a>
(default: $<a href="postconf.5.html#default_transport">default_transport</a>)</b></DT><DD>

<p>
Overrides the <a href="postconf.5.html#default_transport">default_transport</a> parameter setting for address
verification probes.
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>


</DD>

<DT><b><a name="address_verify_local_transport">address_verify_local_transport</a>
(default: $<a href="postconf.5.html#local_transport">local_transport</a>)</b></DT><DD>

<p>
Overrides the <a href="postconf.5.html#local_transport">local_transport</a> parameter setting for address
verification probes.
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>


</DD>

<DT><b><a name="address_verify_map">address_verify_map</a>
(default: empty)</b></DT><DD>

<p>
Optional lookup table for persistent address verification status
storage.  The table is maintained by the <a href="verify.8.html">verify(8)</a> service, and
is opened before the process releases privileges.
</p>

<p>
By default, the information is kept in volatile memory, and is lost
after "<b>postfix reload</b>" or "<b>postfix stop</b>".
</p>

<p>
Specify a location in a file system that will not fill up. If the
database becomes corrupted, the world comes to an end. To recover
delete the file and do "<b>postfix reload</b>".
</p>

<p> As of version 2.5, Postfix no longer uses root privileges when
opening this file. The file should now be stored under the Postfix-owned
<a href="postconf.5.html#data_directory">data_directory</a>. As a migration aid, an attempt to open the file
under a non-Postfix directory is redirected to the Postfix-owned
<a href="postconf.5.html#data_directory">data_directory</a>, and a warning is logged. </p>

<p>
Examples:
</p>

<pre>
<a href="postconf.5.html#address_verify_map">address_verify_map</a> = hash:/var/lib/postfix/verify
<a href="postconf.5.html#address_verify_map">address_verify_map</a> = btree:/var/lib/postfix/verify
</pre>

<p>
This feature is available in Postfix 2.1 and later.
</p>


</DD>

<DT><b><a name="address_verify_negative_cache">address_verify_negative_cache</a>
(default: yes)</b></DT><DD>

<p>
Enable caching of failed address verification probe results.  When
this feature is enabled, the cache may pollute quickly with garbage.
When this feature is disabled, Postfix will generate an address
probe for every lookup.
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>


</DD>

<DT><b><a name="address_verify_negative_expire_time">address_verify_negative_expire_time</a>
(default: 3d)</b></DT><DD>

<p>
The time after which a failed probe expires from the address
verification cache.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>


</DD>

<DT><b><a name="address_verify_negative_refresh_time">address_verify_negative_refresh_time</a>
(default: 3h)</b></DT><DD>

<p>
The time after which a failed address verification probe needs to
be refreshed.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>


</DD>

<DT><b><a name="address_verify_poll_count">address_verify_poll_count</a>
(default: 3)</b></DT><DD>

<p>
How many times to query the <a href="verify.8.html">verify(8)</a> service for the completion
of an address verification request in progress.
</p>

<p>
The default poll count is 3.
</p>

<p>
Specify 1 to implement a crude form of greylisting, that is, always
defer the first delivery request for a never seen before address.
</p>

<p>
Example:
</p>

<pre>
<a href="postconf.5.html#address_verify_poll_count">address_verify_poll_count</a> = 1
</pre>

<p>
This feature is available in Postfix 2.1 and later.
</p>


</DD>

<DT><b><a name="address_verify_poll_delay">address_verify_poll_delay</a>
(default: 3s)</b></DT><DD>

<p>
The delay between queries for the completion of an address
verification request in progress.
</p>

<p>
The default polling delay is 3 seconds.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>


</DD>

<DT><b><a name="address_verify_positive_expire_time">address_verify_positive_expire_time</a>
(default: 31d)</b></DT><DD>

<p>
The time after which a successful probe expires from the address
verification cache.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>


</DD>

<DT><b><a name="address_verify_positive_refresh_time">address_verify_positive_refresh_time</a>
(default: 7d)</b></DT><DD>

<p>
The time after which a successful address verification probe needs
to be refreshed.  The address verification status is not updated
when the probe fails (optimistic caching).
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>


</DD>

<DT><b><a name="address_verify_relay_transport">address_verify_relay_transport</a>
(default: $<a href="postconf.5.html#relay_transport">relay_transport</a>)</b></DT><DD>

<p>
Overrides the <a href="postconf.5.html#relay_transport">relay_transport</a> parameter setting for address
verification probes.
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>


</DD>

<DT><b><a name="address_verify_relayhost">address_verify_relayhost</a>
(default: $<a href="postconf.5.html#relayhost">relayhost</a>)</b></DT><DD>

<p>
Overrides the <a href="postconf.5.html#relayhost">relayhost</a> parameter setting for address verification
probes. This information can be overruled with the <a href="transport.5.html">transport(5)</a> table.
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>


</DD>

<DT><b><a name="address_verify_sender">address_verify_sender</a>
(default: $<a href="postconf.5.html#double_bounce_sender">double_bounce_sender</a>)</b></DT><DD>

<p> The sender address to use in address verification probes; prior
to Postfix 2.5 the default was "postmaster". To
avoid problems with address probes that are sent in response to
address probes, the Postfix SMTP server excludes the probe sender
address from all SMTPD access blocks. </p>

<p>
Specify an empty value (<a href="postconf.5.html#address_verify_sender">address_verify_sender</a> =) or &lt;&gt; if you want
to use the null sender address. Beware, some sites reject mail from
&lt;&gt;, even though RFCs require that such addresses be accepted.
</p>

<p>
Examples:
</p>

<pre>
<a href="postconf.5.html#address_verify_sender">address_verify_sender</a> = &lt;&gt;
<a href="postconf.5.html#address_verify_sender">address_verify_sender</a> = postmaster@my.domain
</pre>

<p>
This feature is available in Postfix 2.1 and later.
</p>


</DD>

<DT><b><a name="address_verify_sender_dependent_relayhost_maps">address_verify_sender_dependent_relayhost_maps</a>
(default: $<a href="postconf.5.html#sender_dependent_relayhost_maps">sender_dependent_relayhost_maps</a>)</b></DT><DD>

<p>
Overrides the <a href="postconf.5.html#sender_dependent_relayhost_maps">sender_dependent_relayhost_maps</a> parameter setting for address
verification probes.
</p>

<p>
This feature is available in Postfix 2.3 and later.
</p>


</DD>

<DT><b><a name="address_verify_service_name">address_verify_service_name</a>
(default: verify)</b></DT><DD>

<p>
The name of the <a href="verify.8.html">verify(8)</a> address verification service. This service
maintains the status of sender and/or recipient address verification
probes, and generates probes on request by other Postfix processes.
</p>


</DD>

<DT><b><a name="address_verify_transport_maps">address_verify_transport_maps</a>
(default: $<a href="postconf.5.html#transport_maps">transport_maps</a>)</b></DT><DD>

<p>
Overrides the <a href="postconf.5.html#transport_maps">transport_maps</a> parameter setting for address verification
probes.
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>


</DD>

<DT><b><a name="address_verify_virtual_transport">address_verify_virtual_transport</a>
(default: $<a href="postconf.5.html#virtual_transport">virtual_transport</a>)</b></DT><DD>

<p>
Overrides the <a href="postconf.5.html#virtual_transport">virtual_transport</a> parameter setting for address
verification probes.
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>


</DD>

<DT><b><a name="alias_database">alias_database</a>
(default: see "postconf -d" output)</b></DT><DD>

<p>
The alias databases for <a href="local.8.html">local(8)</a> delivery that are updated with
"<b>newaliases</b>" or with "<b>sendmail -bi</b>".
</p>

<p>
This is a separate configuration parameter because not all the
tables specified with $<a href="postconf.5.html#alias_maps">alias_maps</a> have to be local files.
</p>

<p>
Examples:
</p>

<pre>
<a href="postconf.5.html#alias_database">alias_database</a> = hash:/etc/aliases
<a href="postconf.5.html#alias_database">alias_database</a> = hash:/etc/mail/aliases
</pre>


</DD>

<DT><b><a name="alias_maps">alias_maps</a>
(default: see "postconf -d" output)</b></DT><DD>

<p>
The alias databases that are used for <a href="local.8.html">local(8)</a> delivery. See
<a href="aliases.5.html">aliases(5)</a> for syntax details.
</p>

<p>
The default list is system dependent.  On systems with NIS, the
default is to search the local alias database, then the NIS alias
database.
</p>

<p>
If you change the alias database, run "<b>postalias /etc/aliases</b>"
(or wherever your system stores the mail alias file), or simply
run "<b>newaliases</b>" to build the necessary DBM or DB file.
</p>

<p>
The <a href="local.8.html">local(8)</a> delivery agent disallows regular expression substitution
of $1 etc. in <a href="postconf.5.html#alias_maps">alias_maps</a>, because that would open a security hole.
</p>

<p>
The <a href="local.8.html">local(8)</a> delivery agent will silently ignore requests to use
the <a href="proxymap.8.html">proxymap(8)</a> server within <a href="postconf.5.html#alias_maps">alias_maps</a>. Instead it will open the
table directly. Before Postfix version 2.2, the <a href="local.8.html">local(8)</a> delivery
agent will terminate with a fatal error.
</p>

<p>
Examples:
</p>

<pre>
<a href="postconf.5.html#alias_maps">alias_maps</a> = hash:/etc/aliases, nis:mail.aliases
<a href="postconf.5.html#alias_maps">alias_maps</a> = hash:/etc/aliases
</pre>


</DD>

<DT><b><a name="allow_mail_to_commands">allow_mail_to_commands</a>
(default: alias, forward)</b></DT><DD>

<p>
Restrict <a href="local.8.html">local(8)</a> mail delivery to external commands.  The default
is to disallow delivery to "|command" in :include:  files (see
<a href="aliases.5.html">aliases(5)</a> for the text that defines this terminology).
</p>

<p>
Specify zero or more of: <b>alias</b>, <b>forward</b> or <b>include</b>,
in order to allow commands in <a href="aliases.5.html">aliases(5)</a>, .forward files or in
:include:  files, respectively.
</p>

<p>
Example:
</p>

<pre>
<a href="postconf.5.html#allow_mail_to_commands">allow_mail_to_commands</a> = alias,forward,include
</pre>


</DD>

<DT><b><a name="allow_mail_to_files">allow_mail_to_files</a>
(default: alias, forward)</b></DT><DD>

<p>
Restrict <a href="local.8.html">local(8)</a> mail delivery to external files. The default is
to disallow "/file/name" destinations in :include:  files (see
<a href="aliases.5.html">aliases(5)</a> for the text that defines this terminology).
</p>

<p>
Specify zero or more of: <b>alias</b>, <b>forward</b> or <b>include</b>,
in order to allow "/file/name" destinations in <a href="aliases.5.html">aliases(5)</a>, .forward
files and in :include:  files, respectively.
</p>

<p>
Example:
</p>

<pre>
<a href="postconf.5.html#allow_mail_to_files">allow_mail_to_files</a> = alias,forward,include
</pre>


</DD>

<DT><b><a name="allow_min_user">allow_min_user</a>
(default: no)</b></DT><DD>

<p>
Allow a sender or recipient address to have `-' as the first
character.  By
default, this is not allowed, to avoid accidents with software that
passes email addresses via the command line. Such software
would not be able to distinguish a malicious address from a
bona fide command-line option. Although this can be prevented by
inserting a "--" option terminator into the command line, this is
difficult to enforce consistently and globally.  </p>

<p> As of Postfix version 2.5, this feature is implemented by
<a href="trivial-rewrite.8.html">trivial-rewrite(8)</a>.  With earlier versions this feature was implemented
by <a href="qmgr.8.html">qmgr(8)</a> and was limited to recipient addresses only. </p>


</DD>

<DT><b><a name="allow_percent_hack">allow_percent_hack</a>
(default: yes)</b></DT><DD>

<p>
Enable the rewriting of the form "user%domain" to "user@domain".
This is enabled by default.
</p>

<p> Note: with Postfix version 2.2, message header address rewriting
happens only when one of the following conditions is true: </p>

<ul>

<li> The message is received with the Postfix <a href="sendmail.1.html">sendmail(1)</a> command,

<li> The message is received from a network client that matches
$<a href="postconf.5.html#local_header_rewrite_clients">local_header_rewrite_clients</a>,

<li> The message is received from the network, and the
<a href="postconf.5.html#remote_header_rewrite_domain">remote_header_rewrite_domain</a> parameter specifies a non-empty value.

</ul>

<p> To get the behavior before Postfix version 2.2, specify
"<a href="postconf.5.html#local_header_rewrite_clients">local_header_rewrite_clients</a> = static:all". </p>

<p>
Example:
</p>

<pre>
<a href="postconf.5.html#allow_percent_hack">allow_percent_hack</a> = no
</pre>


</DD>

<DT><b><a name="allow_untrusted_routing">allow_untrusted_routing</a>
(default: no)</b></DT><DD>

<p>
Forward mail with sender-specified routing (user[@%!]remote[@%!]site)
from untrusted clients to destinations matching $<a href="postconf.5.html#relay_domains">relay_domains</a>.
</p>

<p>
By default, this feature is turned off.  This closes a nasty open
relay loophole where a backup MX host can be tricked into forwarding
junk mail to a primary MX host which then spams it out to the world.
</p>

<p>
This parameter also controls if non-local addresses with sender-specified
routing can match Postfix access tables. By default, such addresses
cannot match Postfix access tables, because the address is ambiguous.
</p>


</DD>

<DT><b><a name="alternate_config_directories">alternate_config_directories</a>
(default: empty)</b></DT><DD>

<p>
A list of non-default Postfix configuration directories that may
be specified with "-c <a href="postconf.5.html#config_directory">config_directory</a>" on the command line, or
via the MAIL_CONFIG environment parameter.
</p>

<p>
This list must be specified in the default Postfix configuration
directory, and is used by set-gid Postfix commands such as <a href="postqueue.1.html">postqueue(1)</a>
and <a href="postdrop.1.html">postdrop(1)</a>.
</p>


</DD>

<DT><b><a name="always_bcc">always_bcc</a>
(default: empty)</b></DT><DD>

<p>
Optional address that receives a "blind carbon copy" of each message
that is received by the Postfix mail system.
</p>

<p>
Note: if mail to the BCC address bounces it will be returned to
the sender.
</p>

<p> Note: automatic BCC recipients are produced only for new mail.
To avoid mailer loops, automatic BCC recipients are not generated
for mail that Postfix forwards internally, nor for mail that Postfix
generates itself. </p>


</DD>

<DT><b><a name="anvil_rate_time_unit">anvil_rate_time_unit</a>
(default: 60s)</b></DT><DD>

<p>
The time unit over which client connection rates and other rates
are calculated.
</p>

<p>
This feature is implemented by the <a href="anvil.8.html">anvil(8)</a> service which is available
in Postfix version 2.2 and later.
</p>

<p>
The default interval is relatively short. Because of the high
frequency of updates, the <a href="anvil.8.html">anvil(8)</a> server uses volatile memory
only. Thus, information is lost whenever the process terminates.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>


</DD>

<DT><b><a name="anvil_status_update_time">anvil_status_update_time</a>
(default: 600s)</b></DT><DD>

<p>
How frequently the <a href="anvil.8.html">anvil(8)</a> connection and rate limiting server
logs peak usage information.
</p>

<p>
This feature is available in Postfix 2.2 and later.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>


</DD>

<DT><b><a name="append_at_myorigin">append_at_myorigin</a>
(default: yes)</b></DT><DD>

<p>
With locally submitted mail, append the string "@$<a href="postconf.5.html#myorigin">myorigin</a>" to mail
addresses without domain information. With remotely submitted mail,
append the string "@$<a href="postconf.5.html#remote_header_rewrite_domain">remote_header_rewrite_domain</a>" instead.
</p>

<p>
Note 1: this feature is enabled by default and must not be turned off.
Postfix does not support domain-less addresses.
</p>

<p> Note 2: with Postfix version 2.2, message header address rewriting
happens only when one of the following conditions is true: </p>

<ul>

<li> The message is received with the Postfix <a href="sendmail.1.html">sendmail(1)</a> command,

<li> The message is received from a network client that matches
$<a href="postconf.5.html#local_header_rewrite_clients">local_header_rewrite_clients</a>,

<li> The message is received from the network, and the
<a href="postconf.5.html#remote_header_rewrite_domain">remote_header_rewrite_domain</a> parameter specifies a non-empty value.

</ul>

<p> To get the behavior before Postfix version 2.2, specify
"<a href="postconf.5.html#local_header_rewrite_clients">local_header_rewrite_clients</a> = static:all". </p>


</DD>

<DT><b><a name="append_dot_mydomain">append_dot_mydomain</a>
(default: yes)</b></DT><DD>

<p>
With locally submitted mail, append the string ".$<a href="postconf.5.html#mydomain">mydomain</a>" to
addresses that have no ".domain" information. With remotely submitted
mail, append the string ".$<a href="postconf.5.html#remote_header_rewrite_domain">remote_header_rewrite_domain</a>"
instead.
</p>

<p>
Note 1: this feature is enabled by default. If disabled, users will not be
able to send mail to "user@partialdomainname" but will have to
specify full domain names instead.
</p>

<p> Note 2: with Postfix version 2.2, message header address rewriting
happens only when one of the following conditions is true: </p>

<ul>

<li> The message is received with the Postfix <a href="sendmail.1.html">sendmail(1)</a> command,

<li> The message is received from a network client that matches
$<a href="postconf.5.html#local_header_rewrite_clients">local_header_rewrite_clients</a>,

<li> The message is received from the network, and the
<a href="postconf.5.html#remote_header_rewrite_domain">remote_header_rewrite_domain</a> parameter specifies a non-empty value.

</ul>

<p> To get the behavior before Postfix version 2.2, specify
"<a href="postconf.5.html#local_header_rewrite_clients">local_header_rewrite_clients</a> = static:all". </p>


</DD>

<DT><b><a name="application_event_drain_time">application_event_drain_time</a>
(default: 100s)</b></DT><DD>

<p>
How long the <a href="postkick.1.html">postkick(1)</a> command waits for a request to enter the
server's input buffer before giving up.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>


</DD>

<DT><b><a name="authorized_flush_users">authorized_flush_users</a>
(default: static:anyone)</b></DT><DD>

<p>
List of users who are authorized to flush the queue.
</p>

<p>
By default, all users are allowed to flush the queue.  Access is
always granted if the invoking user is the super-user or the
$<a href="postconf.5.html#mail_owner">mail_owner</a> user.  Otherwise, the real UID of the process is looked
up in the system password file, and access is granted only if the
corresponding login name is on the access list.  The username
"unknown" is used for processes whose real UID is not found in the
password file.  </p>

<p>
Specify a list of user names, "/file/name" or "<a href="DATABASE_README.html">type:table</a>" patterns,
separated by commas and/or whitespace. The list is matched left to
right, and the search stops on the first match. A "/file/name"
pattern is replaced
by its contents; a "<a href="DATABASE_README.html">type:table</a>" lookup table is matched when a name
matches a lookup key (the lookup result is ignored).  Continue long
lines by starting the next line with whitespace. Specify "!pattern"
to exclude a name from the list. The form "!/file/name" is supported
only in Postfix version 2.4 and later.  </p>

<p>
This feature is available in Postfix 2.2 and later.
</p>


</DD>

<DT><b><a name="authorized_mailq_users">authorized_mailq_users</a>
(default: static:anyone)</b></DT><DD>

<p>
List of users who are authorized to view the queue.
</p>

<p>
By default, all users are allowed to view the queue.  Access is
always granted if the invoking user is the super-user or the
$<a href="postconf.5.html#mail_owner">mail_owner</a> user.  Otherwise, the real UID of the process is looked
up in the system password file, and access is granted only if the
corresponding login name is on the access list.  The username
"unknown" is used for processes whose real UID is not found in the
password file.  </p>

<p>
Specify a list of user names, "/file/name" or "<a href="DATABASE_README.html">type:table</a>" patterns,
separated by commas and/or whitespace. The list is matched left to
right, and the search stops on the first match. A "/file/name"
pattern is replaced
by its contents; a "<a href="DATABASE_README.html">type:table</a>" lookup table is matched when a name
matches a lookup key (the lookup result is ignored).  Continue long
lines by starting the next line with whitespace. Specify "!pattern"
to exclude a user name from the list. The form "!/file/name" is
supported only in Postfix version 2.4 and later.  </p>

<p>
This feature is available in Postfix 2.2 and later.
</p>


</DD>

<DT><b><a name="authorized_submit_users">authorized_submit_users</a>
(default: static:anyone)</b></DT><DD>

<p>
List of users who are authorized to submit mail with the <a href="sendmail.1.html">sendmail(1)</a>
command (and with the privileged <a href="postdrop.1.html">postdrop(1)</a> helper command).
</p>

<p>
By default, all users are allowed to submit mail.  Otherwise, the
real UID of the process is looked up in the system password file,
and access is granted only if the corresponding login name is on
the access list.  The username "unknown" is used for processes
whose real UID is not found in the password file. To deny mail
submission access to all users specify an empty list.  </p>

<p>
Specify a list of user names, "/file/name" or "<a href="DATABASE_README.html">type:table</a>" patterns,
separated by commas and/or whitespace. The list is matched left to right,
and the search stops on the first match. A "/file/name" pattern is
replaced by its contents;
a "<a href="DATABASE_README.html">type:table</a>" lookup table is matched when a name matches a lookup key
(the lookup result is ignored).  Continue long lines by starting the
next line with whitespace. Specify "!pattern" to exclude a user
name from the list. The form "!/file/name" is supported only in
Postfix version 2.4 and later.  </p>

<p>
Example:
</p>

<pre>
<a href="postconf.5.html#authorized_submit_users">authorized_submit_users</a> = !www, static:all
</pre>

<p>
This feature is available in Postfix 2.2 and later.
</p>


</DD>

<DT><b><a name="authorized_verp_clients">authorized_verp_clients</a>
(default: $<a href="postconf.5.html#mynetworks">mynetworks</a>)</b></DT><DD>

<p> What SMTP clients are allowed to specify the XVERP command.
This command requests that mail be delivered one recipient at a
time with a per recipient return address.  </p>

<p> By default, only trusted clients are allowed to specify XVERP.
</p>

<p> This parameter was introduced with Postfix version 1.1.  Postfix
version 2.1 renamed this parameter to <a href="postconf.5.html#smtpd_authorized_verp_clients">smtpd_authorized_verp_clients</a>
and changed the default to none. </p>

<p> Specify a list of network/netmask patterns, separated by commas
and/or whitespace. The mask specifies the number of bits in the
network part of a host address. You can also specify hostnames or
.domain names (the initial dot causes the domain to match any name
below it),  "/file/name" or "<a href="DATABASE_README.html">type:table</a>" patterns.  A "/file/name"
pattern is replaced by its contents; a "<a href="DATABASE_README.html">type:table</a>" lookup table
is matched when a table entry matches a lookup string (the lookup
result is ignored).  Continue long lines by starting the next line
with whitespace. Specify "!pattern" to exclude an address or network
block from the list. The form "!/file/name" is supported only in
Postfix version 2.4 and later. </p>

<p> Note: IP version 6 address information must be specified inside
<tt>[]</tt> in the <a href="postconf.5.html#authorized_verp_clients">authorized_verp_clients</a> value, and in files
specified with "/file/name".  IP version 6 addresses contain the
":" character, and would otherwise be confused with a "<a href="DATABASE_README.html">type:table</a>"
pattern.  </p>


</DD>

<DT><b><a name="backwards_bounce_logfile_compatibility">backwards_bounce_logfile_compatibility</a>
(default: yes)</b></DT><DD>

<p>
Produce additional <a href="bounce.8.html">bounce(8)</a> logfile records that can be read by
Postfix versions before 2.0. The current and more extensible "name =
value" format is needed in order to implement more sophisticated
functionality.
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>


</DD>

<DT><b><a name="berkeley_db_create_buffer_size">berkeley_db_create_buffer_size</a>
(default: 16777216)</b></DT><DD>

<p>
The per-table I/O buffer size for programs that create Berkeley DB
hash or btree tables.  Specify a byte count.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>


</DD>

<DT><b><a name="berkeley_db_read_buffer_size">berkeley_db_read_buffer_size</a>
(default: 131072)</b></DT><DD>

<p>
The per-table I/O buffer size for programs that read Berkeley DB
hash or btree tables.  Specify a byte count.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>


</DD>

<DT><b><a name="best_mx_transport">best_mx_transport</a>
(default: empty)</b></DT><DD>

<p>
Where the Postfix SMTP client should deliver mail when it detects
a "mail loops back to myself" error condition. This happens when
the local MTA is the best SMTP mail exchanger for a destination
not listed in $<a href="postconf.5.html#mydestination">mydestination</a>, $<a href="postconf.5.html#inet_interfaces">inet_interfaces</a>, $<a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a>,
$<a href="postconf.5.html#virtual_alias_domains">virtual_alias_domains</a>, or $<a href="postconf.5.html#virtual_mailbox_domains">virtual_mailbox_domains</a>.  By default,
the Postfix SMTP client returns such mail as undeliverable.
</p>

<p>
Specify, for example, "<a href="postconf.5.html#best_mx_transport">best_mx_transport</a> = local" to pass the mail
from the Postfix SMTP client to the <a href="local.8.html">local(8)</a> delivery agent. You
can specify
any message delivery "transport" or "transport:nexthop" that is
defined in the <a href="master.5.html">master.cf</a> file. See the <a href="transport.5.html">transport(5)</a> manual page
for the syntax and meaning of "transport" or "transport:nexthop".
</p>

<p>
However, this feature is expensive because it ties up a Postfix
SMTP client process while the <a href="local.8.html">local(8)</a> delivery agent is doing its
work. It is more efficient (for Postfix) to list all <a href="VIRTUAL_README.html#canonical">hosted domains</a>
in a table or database.
</p>


</DD>

<DT><b><a name="biff">biff</a>
(default: yes)</b></DT><DD>

<p>
Whether or not to use the local <a href="postconf.5.html#biff">biff</a> service.  This service sends
"new mail" notifications to users who have requested new mail
notification with the UNIX command "<a href="postconf.5.html#biff">biff</a> y".
</p>

<p>
For compatibility reasons this feature is on by default.  On systems
with lots of interactive users, the <a href="postconf.5.html#biff">biff</a> service can be a performance
drain.  Specify "<a href="postconf.5.html#biff">biff</a> = no" in <a href="postconf.5.html">main.cf</a> to disable.
</p>


</DD>

<DT><b><a name="body_checks">body_checks</a>
(default: empty)</b></DT><DD>

<p> Optional lookup tables for content inspection as specified in
the <a href="header_checks.5.html">body_checks(5)</a> manual page.  </p>

<p> Note: with Postfix versions before 2.0, these rules inspect
all content after the primary message headers. </p>


</DD>

<DT><b><a name="body_checks_size_limit">body_checks_size_limit</a>
(default: 51200)</b></DT><DD>

<p>
How much text in a message body segment (or attachment, if you
prefer to use that term) is subjected to <a href="postconf.5.html#body_checks">body_checks</a> inspection.
The amount of text is limited to avoid scanning huge attachments.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>


</DD>

<DT><b><a name="bounce_notice_recipient">bounce_notice_recipient</a>
(default: postmaster)</b></DT><DD>

<p>
The recipient of postmaster notifications with the message headers
of mail that Postfix did not deliver and of SMTP conversation
transcripts of mail that Postfix did not receive.  This feature is
enabled with the <a href="postconf.5.html#notify_classes">notify_classes</a> parameter.  </p>


</DD>

<DT><b><a name="bounce_queue_lifetime">bounce_queue_lifetime</a>
(default: 5d)</b></DT><DD>

<p>
The maximal time a bounce message is queued before it is considered
undeliverable.  By default, this is the same as the queue life time
for regular mail.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is d (days).
</p>

<p>
Specify 0 when mail delivery should be tried only once.
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>


</DD>

<DT><b><a name="bounce_service_name">bounce_service_name</a>
(default: bounce)</b></DT><DD>

<p>
The name of the <a href="bounce.8.html">bounce(8)</a> service. This service maintains a record
of failed delivery attempts and generates non-delivery notifications.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>


</DD>

<DT><b><a name="bounce_size_limit">bounce_size_limit</a>
(default: 50000)</b></DT><DD>

<p> The maximal amount of original message text that is sent in a
non-delivery notification. Specify a byte count. If you increase
this limit, then you should increase the <a href="postconf.5.html#mime_nesting_limit">mime_nesting_limit</a> value
proportionally.  </p>


</DD>

<DT><b><a name="bounce_template_file">bounce_template_file</a>
(default: empty)</b></DT><DD>

<p> Pathname of a configuration file with bounce message templates.
These override the built-in templates of delivery status notification
(DSN) messages for undeliverable mail, for delayed mail, successful
delivery, or delivery verification. The <a href="bounce.5.html">bounce(5)</a> manual page
describes how to edit and test template files.  </p>

<p> Template message body text may contain $name references to
Postfix configuration parameters. The result of $name expansion can
be previewed with "<b>postconf -b <i>file_name</i></b>" before the file
is placed into the Postfix configuration directory.  </p>

<p> This feature is available in Postfix 2.3 and later.  </p>


</DD>

<DT><b><a name="broken_sasl_auth_clients">broken_sasl_auth_clients</a>
(default: no)</b></DT><DD>

<p>
Enable inter-operability with SMTP clients that implement an obsolete
version of the AUTH command (<a href="http://tools.ietf.org/html/rfc4954">RFC 4954</a>). Examples of such clients
are MicroSoft Outlook Express version 4 and MicroSoft Exchange
version 5.0.
</p>

<p>
Specify "<a href="postconf.5.html#broken_sasl_auth_clients">broken_sasl_auth_clients</a> = yes" to have Postfix advertise
AUTH support in a non-standard way.
</p>


</DD>

<DT><b><a name="canonical_classes">canonical_classes</a>
(default: envelope_sender, envelope_recipient, header_sender, header_recipient)</b></DT><DD>

<p> What addresses are subject to <a href="postconf.5.html#canonical_maps">canonical_maps</a> address mapping.
By default, <a href="postconf.5.html#canonical_maps">canonical_maps</a> address mapping is applied to envelope
sender and recipient addresses, and to header sender and header
recipient addresses.  </p>

<p> Specify one or more of: envelope_sender, envelope_recipient,
header_sender, header_recipient </p>

<p> This feature is available in Postfix 2.2 and later. </p>


</DD>

<DT><b><a name="canonical_maps">canonical_maps</a>
(default: empty)</b></DT><DD>

<p>
Optional address mapping lookup tables for message headers and
envelopes. The mapping is applied to both sender and recipient
addresses, in both envelopes and in headers, as controlled
with the <a href="postconf.5.html#canonical_classes">canonical_classes</a> parameter. This is typically used
to clean up dirty addresses from legacy mail systems, or to replace
login names by Firstname.Lastname.  The table format and lookups
are documented in <a href="canonical.5.html">canonical(5)</a>. For an overview of Postfix address
manipulations see the <a href="ADDRESS_REWRITING_README.html">ADDRESS_REWRITING_README</a> document.
</p>

<p>
If you use this feature, run "<b>postmap /etc/postfix/canonical</b>" to
build the necessary DBM or DB file after every change. The changes
will become visible after a minute or so.  Use "<b>postfix reload</b>"
to eliminate the delay.
</p>

<p> Note: with Postfix version 2.2, message header address mapping
happens only when message header address rewriting is enabled: </p>

<ul>

<li> The message is received with the Postfix <a href="sendmail.1.html">sendmail(1)</a> command,

<li> The message is received from a network client that matches
$<a href="postconf.5.html#local_header_rewrite_clients">local_header_rewrite_clients</a>,

<li> The message is received from the network, and the
<a href="postconf.5.html#remote_header_rewrite_domain">remote_header_rewrite_domain</a> parameter specifies a non-empty value.

</ul>

<p> To get the behavior before Postfix version 2.2, specify
"<a href="postconf.5.html#local_header_rewrite_clients">local_header_rewrite_clients</a> = static:all". </p>

<p>
Examples:
</p>

<pre>
<a href="postconf.5.html#canonical_maps">canonical_maps</a> = dbm:/etc/postfix/canonical
<a href="postconf.5.html#canonical_maps">canonical_maps</a> = hash:/etc/postfix/canonical
</pre>


</DD>

<DT><b><a name="cleanup_service_name">cleanup_service_name</a>
(default: cleanup)</b></DT><DD>

<p>
The name of the <a href="cleanup.8.html">cleanup(8)</a> service. This service rewrites addresses
into the standard form, and performs <a href="canonical.5.html">canonical(5)</a> address mapping
and <a href="virtual.5.html">virtual(5)</a> aliasing.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>


</DD>

<DT><b><a name="command_directory">command_directory</a>
(default: see "postconf -d" output)</b></DT><DD>

<p>
The location of all postfix administrative commands.
</p>


</DD>

<DT><b><a name="command_execution_directory">command_execution_directory</a>
(default: empty)</b></DT><DD>

<p> The <a href="local.8.html">local(8)</a> delivery agent working directory for delivery to
external command.  Failure to change directory causes the delivery
to be deferred. </p>

<p> The following $name expansions are done on <a href="postconf.5.html#command_execution_directory">command_execution_directory</a>
before the directory is changed. Expansion happens in the context
of the delivery request.  The result of $name expansion is filtered
with the character set that is specified with the
<a href="postconf.5.html#execution_directory_expansion_filter">execution_directory_expansion_filter</a> parameter.  </p>

<dl>

<dt><b>$user</b></dt>

<dd>The recipient's username. </dd>

<dt><b>$shell</b></dt>

<dd>The recipient's login shell pathname. </dd>

<dt><b>$home</b></dt>

<dd>The recipient's home directory. </dd>

<dt><b>$recipient</b></dt>

<dd>The full recipient address. </dd>

<dt><b>$extension</b></dt>

<dd>The optional recipient address extension. </dd>

<dt><b>$domain</b></dt>

<dd>The recipient domain. </dd>

<dt><b>$local</b></dt>

<dd>The entire recipient localpart. </dd>

<dt><b>$<a href="postconf.5.html#recipient_delimiter">recipient_delimiter</a></b></dt>

<dd>The system-wide recipient address extension delimiter. </dd>

<dt><b>${name?value}</b></dt>

<dd>Expands to <i>value</i> when <i>$name</i> is non-empty. </dd>

<dt><b>${name:value}</b></dt>

<dd>Expands to <i>value</i> when <i>$name</i> is empty. </dd>

</dl>

<p>
Instead of $name you can also specify ${name} or $(name).
</p>

<p> This feature is available in Postfix 2.2 and later. </p>


</DD>

<DT><b><a name="command_expansion_filter">command_expansion_filter</a>
(default: see "postconf -d" output)</b></DT><DD>

<p>
Restrict the characters that the <a href="local.8.html">local(8)</a> delivery agent allows in
$name expansions of $<a href="postconf.5.html#mailbox_command">mailbox_command</a> and $<a href="postconf.5.html#command_execution_directory">command_execution_directory</a>.
Characters outside the
allowed set are replaced by underscores.
</p>


</DD>

<DT><b><a name="command_time_limit">command_time_limit</a>
(default: 1000s)</b></DT><DD>

<p>
Time limit for delivery to external commands. This limit is used
by the <a href="local.8.html">local(8)</a> delivery agent, and is the default time limit for
delivery by the <a href="pipe.8.html">pipe(8)</a> delivery agent.
</p>

<p>
Note: if you set this time limit to a large value you must update the
global <a href="postconf.5.html#ipc_timeout">ipc_timeout</a> parameter as well.
</p>


</DD>

<DT><b><a name="config_directory">config_directory</a>
(default: see "postconf -d" output)</b></DT><DD>

<p> The default location of the Postfix <a href="postconf.5.html">main.cf</a> and <a href="master.5.html">master.cf</a>
configuration files. This can be overruled via the following
mechanisms: </p>

<ul>

<li> <p> The MAIL_CONFIG environment variable (daemon processes
and commands). </p>

<li> <p> The "-c" command-line option (commands only). </p>

</ul>

<p> With Postfix command that run with set-gid privileges, a
<a href="postconf.5.html#config_directory">config_directory</a> override requires either root privileges, or it
requires that the directory is listed with the <a href="postconf.5.html#alternate_config_directories">alternate_config_directories</a>
parameter in the default <a href="postconf.5.html">main.cf</a> file.  </p>


</DD>

<DT><b><a name="connection_cache_protocol_timeout">connection_cache_protocol_timeout</a>
(default: 5s)</b></DT><DD>

<p> Time limit for connection cache connect, send or receive
operations.  The time limit is enforced in the client. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="connection_cache_service_name">connection_cache_service_name</a>
(default: scache)</b></DT><DD>

<p> The name of the <a href="scache.8.html">scache(8)</a> connection cache service.  This service
maintains a limited pool of cached sessions.  </p>


</DD>

<DT><b><a name="connection_cache_status_update_time">connection_cache_status_update_time</a>
(default: 600s)</b></DT><DD>

<p> How frequently the <a href="scache.8.html">scache(8)</a> server logs usage statistics with
connection cache hit and miss rates for logical destinations and for
physical endpoints. </p>


</DD>

<DT><b><a name="connection_cache_ttl_limit">connection_cache_ttl_limit</a>
(default: 2s)</b></DT><DD>

<p> The maximal time-to-live value that the <a href="scache.8.html">scache(8)</a> connection
cache server
allows. Requests that specify a larger TTL will be stored with the
maximum allowed TTL. The purpose of this additional control is to
protect the infrastructure against careless people. The cache TTL
is already bounded by $<a href="postconf.5.html#max_idle">max_idle</a>.  </p>


</DD>

<DT><b><a name="content_filter">content_filter</a>
(default: empty)</b></DT><DD>

<p>
The name of a mail delivery transport that filters mail after
it is queued.
</p>

<p>
This parameter uses the same syntax as the right-hand side of a
Postfix <a href="transport.5.html">transport(5)</a> table. This setting has a lower precedence
than a content filter that is specified with an <a href="access.5.html">access(5)</a> table or
in a <a href="header_checks.5.html">header_checks(5)</a> or <a href="header_checks.5.html">body_checks(5)</a> table.
</p>


</DD>

<DT><b><a name="cyrus_sasl_config_path">cyrus_sasl_config_path</a>
(default: empty)</b></DT><DD>

<p> Search path for Cyrus SASL application configuration files,
currently used only to locate the $<a href="postconf.5.html#smtpd_sasl_path">smtpd_sasl_path</a>.conf file.
Specify zero or more directories separated by a colon character,
or an empty value to use Cyrus SASL's built-in search path.  </p>

<p> This feature is available in Postfix 2.5 and later when compiled
with Cyrus SASL 2.1.22 or later. </p>


</DD>

<DT><b><a name="daemon_directory">daemon_directory</a>
(default: see "postconf -d" output)</b></DT><DD>

<p>
The directory with Postfix support programs and daemon programs.
These should not be invoked directly by humans. The directory must
be owned by root.
</p>


</DD>

<DT><b><a name="daemon_timeout">daemon_timeout</a>
(default: 18000s)</b></DT><DD>

<p> How much time a Postfix daemon process may take to handle a
request before it is terminated by a built-in watchdog timer.  </p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>


</DD>

<DT><b><a name="data_directory">data_directory</a>
(default: see "postconf -d" output)</b></DT><DD>

<p> The directory with Postfix-writable data files (for example:
caches, pseudo-random numbers).  This directory must be owned by
the <a href="postconf.5.html#mail_owner">mail_owner</a> account, and must not be shared with non-Postfix
software.  </p>

<p> This feature is available in Postfix 2.5 and later. </p>


</DD>

<DT><b><a name="debug_peer_level">debug_peer_level</a>
(default: 2)</b></DT><DD>

<p> The increment in verbose logging level when a remote client or
server matches a pattern in the <a href="postconf.5.html#debug_peer_list">debug_peer_list</a> parameter.  </p>


</DD>

<DT><b><a name="debug_peer_list">debug_peer_list</a>
(default: empty)</b></DT><DD>

<p> Optional list of remote client or server hostname or network
address patterns that cause the verbose logging level to increase
by the amount specified in $<a href="postconf.5.html#debug_peer_level">debug_peer_level</a>.  </p>

<p> Specify domain names, network/netmask patterns, "/file/name"
patterns or "<a href="DATABASE_README.html">type:table</a>" lookup tables. The right-hand side result
from "<a href="DATABASE_README.html">type:table</a>" lookups is ignored.  </p>

<p> Pattern matching of domain names is controlled by the
<a href="postconf.5.html#parent_domain_matches_subdomains">parent_domain_matches_subdomains</a> parameter.  </p>

<p>
Examples:
</p>

<pre>
<a href="postconf.5.html#debug_peer_list">debug_peer_list</a> = 127.0.0.1
<a href="postconf.5.html#debug_peer_list">debug_peer_list</a> = some.domain
</pre>


</DD>

<DT><b><a name="debugger_command">debugger_command</a>
(default: empty)</b></DT><DD>

<p>
The external command to execute when a Postfix daemon program is
invoked with the -D option.
</p>

<p>
Use "command .. &amp; sleep 5" so that the debugger can attach before
the process marches on. If you use an X-based debugger, be sure to
set up your XAUTHORITY environment variable before starting Postfix.
</p>

<p>
Example:
</p>

<pre>
<a href="postconf.5.html#debugger_command">debugger_command</a> =
    PATH=/usr/bin:/usr/X11R6/bin
    ddd $<a href="postconf.5.html#daemon_directory">daemon_directory</a>/$<a href="postconf.5.html#process_name">process_name</a> $<a href="postconf.5.html#process_id">process_id</a> &amp; sleep 5
</pre>


</DD>

<DT><b><a name="default_database_type">default_database_type</a>
(default: see "postconf -d" output)</b></DT><DD>

<p>
The default database type for use in <a href="newaliases.1.html">newaliases(1)</a>, <a href="postalias.1.html">postalias(1)</a>
and <a href="postmap.1.html">postmap(1)</a> commands. On many UNIX systems the default type is
either <b>dbm</b> or <b>hash</b>. The default setting is frozen
when the Postfix system is built.
</p>

<p>
Examples:
</p>

<pre>
<a href="postconf.5.html#default_database_type">default_database_type</a> = hash
<a href="postconf.5.html#default_database_type">default_database_type</a> = dbm
</pre>


</DD>

<DT><b><a name="default_delivery_slot_cost">default_delivery_slot_cost</a>
(default: 5)</b></DT><DD>

<p>
How often the Postfix queue manager's scheduler is allowed to
preempt delivery of one message with another.
</p>

<p>
Each transport maintains a so-called "available delivery slot counter"
for each message. One message can be preempted by another one when
the other message can be delivered using no more delivery slots
(i.e., invocations of delivery agents) than the current message
counter has accumulated (or will eventually accumulate - see about
slot loans below). This parameter controls how often is the counter
incremented - it happens after each <a href="postconf.5.html#default_delivery_slot_cost">default_delivery_slot_cost</a>
recipients have been delivered.
</p>

<p>
The cost of 0 is used to disable the preempting scheduling completely.
The minimum value the scheduling algorithm can use is 2 - use it
if you want to maximize the message throughput rate. Although there
is no maximum, it doesn't make much sense to use values above say
50.
</p>

<p>
The only reason why the value of 2 is not the default is the way
this parameter affects the delivery of mailing-list mail. In the
worst case, their delivery can take somewhere between (cost+1/cost)
and (cost/cost-1) times more than if the preemptive scheduler was
disabled. The default value of 5 turns out to provide reasonable
message response times while making sure the mailing-list deliveries
are not extended by more than 20-25 percent even in the worst case.
</p>

<p> Use <a href="postconf.5.html#transport_delivery_slot_cost"><i>transport</i>_delivery_slot_cost</a> to specify a
transport-specific override, where <i>transport</i> is the <a href="master.5.html">master.cf</a>
name of the message delivery transport.
</p>

<p>
Examples:
</p>

<pre>
<a href="postconf.5.html#default_delivery_slot_cost">default_delivery_slot_cost</a> = 0
<a href="postconf.5.html#default_delivery_slot_cost">default_delivery_slot_cost</a> = 2
</pre>


</DD>

<DT><b><a name="default_delivery_slot_discount">default_delivery_slot_discount</a>
(default: 50)</b></DT><DD>

<p>
The default value for transport-specific _delivery_slot_discount
settings.
</p>

<p>
This parameter speeds up the moment when a message preemption can
happen. Instead of waiting until the full amount of delivery slots
required is available, the preemption can happen when
transport_delivery_slot_discount percent of the required amount
plus transport_delivery_slot_loan still remains to be accumulated.
Note that the full amount will still have to be accumulated before
another preemption can take place later.
</p>

<p> Use <a href="postconf.5.html#transport_delivery_slot_discount"><i>transport</i>_delivery_slot_discount</a> to specify a
transport-specific override, where <i>transport</i> is the <a href="master.5.html">master.cf</a>
name of the message delivery transport.
</p>


</DD>

<DT><b><a name="default_delivery_slot_loan">default_delivery_slot_loan</a>
(default: 3)</b></DT><DD>

<p>
The default value for transport-specific _delivery_slot_loan
settings.
</p>

<p>
This parameter speeds up the moment when a message preemption can
happen. Instead of waiting until the full amount of delivery slots
required is available, the preemption can happen when
transport_delivery_slot_discount percent of the required amount
plus transport_delivery_slot_loan still remains to be accumulated.
Note that the full amount will still have to be accumulated before
another preemption can take place later.
</p>

<p> Use <a href="postconf.5.html#transport_delivery_slot_loan"><i>transport</i>_delivery_slot_loan</a> to specify a
transport-specific override, where <i>transport</i> is the <a href="master.5.html">master.cf</a>
name of the message delivery transport.
</p>


</DD>

<DT><b><a name="default_destination_concurrency_failed_cohort_limit">default_destination_concurrency_failed_cohort_limit</a>
(default: 1)</b></DT><DD>

<p> How many pseudo-cohorts must suffer connection or handshake
failure before a specific destination is considered unavailable
(and further delivery is suspended). Specify zero to disable this
feature. A destination's pseudo-cohort failure count is reset each
time a delivery completes without connection or handshake failure
for that specific destination. </p>

<p> A pseudo-cohort is the number of deliveries equal to a destination's
delivery concurrency. </p>

<p> Use <a href="postconf.5.html#transport_destination_concurrency_failed_cohort_limit"><i>transport</i>_destination_concurrency_failed_cohort_limit</a> to specify
a transport-specific override, where <i>transport</i> is the <a href="master.5.html">master.cf</a>
name of the message delivery transport. </p>

<p> This feature is available in Postfix 2.5. The default setting
is compatible with earlier Postfix versions. </p>


</DD>

<DT><b><a name="default_destination_concurrency_limit">default_destination_concurrency_limit</a>
(default: 20)</b></DT><DD>

<p>
The default maximal number of parallel deliveries to the same
destination.  This is the default limit for delivery via the <a href="lmtp.8.html">lmtp(8)</a>,
<a href="pipe.8.html">pipe(8)</a>, <a href="smtp.8.html">smtp(8)</a> and <a href="virtual.8.html">virtual(8)</a> delivery agents.
With per-destination recipient limit &gt; 1, a destination is a domain,
otherwise it is a recipient.
</p>

<p> Use <a href="postconf.5.html#transport_destination_concurrency_limit"><i>transport</i>_destination_concurrency_limit</a> to specify a
transport-specific override, where <i>transport</i> is the <a href="master.5.html">master.cf</a>
name of the message delivery transport.
</p>


</DD>

<DT><b><a name="default_destination_concurrency_negative_feedback">default_destination_concurrency_negative_feedback</a>
(default: 1)</b></DT><DD>

<p> The per-destination amount of delivery concurrency negative
feedback, after a delivery completes with a connection or handshake
failure. Feedback values are in the range 0..1 inclusive. With
negative feedback, concurrency is decremented at the beginning of
a sequence of length 1/feedback. This is unlike positive feedback,
where concurrency is incremented at the end of a sequence of length
1/feedback. </p>

<p> As of Postfix version 2.5, negative feedback cannot reduce
delivery concurrency to zero.  Instead, a destination is marked
dead (further delivery suspended) after the failed pseudo-cohort
count reaches $<a href="postconf.5.html#default_destination_concurrency_failed_cohort_limit">default_destination_concurrency_failed_cohort_limit</a>
(or $<a href="postconf.5.html#transport_destination_concurrency_failed_cohort_limit"><i>transport</i>_destination_concurrency_failed_cohort_limit</a>).
To make the scheduler completely immune to connection or handshake
failures, specify a zero feedback value and a zero failed pseudo-cohort
limit.  </p>

<p> Specify one of the following forms: </p>

<dl>

<dt> <b><i>number</i> </b> </dt>

<dt> <b><i>number</i> / <i>number</i> </b> </dt>

<dd> Constant feedback. The value must be in the range 0..1 inclusive.
The default setting of "1" is compatible with Postfix versions
before 2.5, where a destination's delivery concurrency is throttled
down to zero (and further delivery suspended) after a single failed
pseudo-cohort. </dd>

<dt> <b><i>number</i> / concurrency </b> </dt>

<dd> Variable feedback of "<i>number</i> / (delivery concurrency)".
The <i>number</i> must be in the range 0..1 inclusive. With
<i>number</i> equal to "1", a destination's delivery concurrency
is decremented by 1 after each failed pseudo-cohort.  </dd>

</dl>

<p> A pseudo-cohort is the number of deliveries equal to a destination's
delivery concurrency. </p>

<p> Use <a href="postconf.5.html#transport_destination_concurrency_positive_feedback"><i>transport</i>_destination_concurrency_negative_feedback</a>
to specify a transport-specific override, where <i>transport</i>
is the <a href="master.5.html">master.cf</a>
name of the message delivery transport. </p>

<p> This feature is available in Postfix 2.5. The default setting
is compatible with earlier Postfix versions. </p>


</DD>

<DT><b><a name="default_destination_concurrency_positive_feedback">default_destination_concurrency_positive_feedback</a>
(default: 1)</b></DT><DD>

<p> The per-destination amount of delivery concurrency positive
feedback, after a delivery completes without connection or handshake
failure. Feedback values are in the range 0..1 inclusive.  The
concurrency increases until it reaches the per-destination maximal
concurrency limit. With positive feedback, concurrency is incremented
at the end of a sequence with length 1/feedback. This is unlike
negative feedback, where concurrency is decremented at the start
of a sequence of length 1/feedback. </p>

<p> Specify one of the following forms:  </p>

<dl>

<dt> <b><i>number</i> </b> </dt>

<dt> <b><i>number</i> / <i>number</i> </b> </dt>

<dd> Constant feedback.  The value must be in the range 0..1
inclusive. The default setting of "1" is compatible with Postfix
versions before 2.5, where a destination's delivery concurrency
doubles after each successful pseudo-cohort.  </dd>

<dt> <b><i>number</i> / concurrency </b> </dt>

<dd> Variable feedback of "<i>number</i> / (delivery concurrency)".
The <i>number</i> must be in the range 0..1 inclusive. With
<i>number</i> equal to "1", a destination's delivery concurrency
is incremented by 1 after each successful pseudo-cohort.  </dd>

</dl>

<p> A pseudo-cohort is the number of deliveries equal to a destination's
delivery concurrency. </p>

<p> Use <a href="postconf.5.html#transport_destination_concurrency_positive_feedback"><i>transport</i>_destination_concurrency_positive_feedback</a>
to specify a transport-specific override, where <i>transport</i>
is the <a href="master.5.html">master.cf</a> name of the message delivery transport. </p>

<p> This feature is available in Postfix 2.5 and later.  </p>


</DD>

<DT><b><a name="default_destination_rate_delay">default_destination_rate_delay</a>
(default: 0s)</b></DT><DD>

<p> The default amount of delay that is inserted between individual
deliveries to the same destination; with per-destination recipient
limit &gt; 1, a destination is a domain, otherwise it is a recipient.
</p>

<p> To enable the delay, specify a non-zero time value (an integral
value plus an optional one-letter suffix that specifies the time
unit). </p>

<p> Time units: s (seconds), m (minutes), h (hours), d (days), w
(weeks). The default time unit is s (seconds). </p>

<p> NOTE: the delay is enforced by the queue manager. The delay
timer state does not survive "postfix reload" or "postfix stop".
</p>

<p> Use <a href="postconf.5.html#transport_destination_rate_delay"><i>transport</i>_destination_rate_delay</a> to specify a
transport-specific override, where <i>transport</i> is the <a href="master.5.html">master.cf</a>
name of the message delivery transport.
</p>

<p> This feature is available in Postfix 2.5 and later. </p>


</DD>

<DT><b><a name="default_destination_recipient_limit">default_destination_recipient_limit</a>
(default: 50)</b></DT><DD>

<p>
The default maximal number of recipients per message delivery.
This is the default limit for delivery via the <a href="lmtp.8.html">lmtp(8)</a>, <a href="pipe.8.html">pipe(8)</a>,
<a href="smtp.8.html">smtp(8)</a> and <a href="virtual.8.html">virtual(8)</a> delivery agents.
</p>

<p> Setting this parameter to a value of 1 changes the meaning of
the corresponding per-destination concurrency limit from concurrency
per domain into concurrency per recipient.  </p>

<p> Use <a href="postconf.5.html#transport_destination_recipient_limit"><i>transport</i>_destination_recipient_limit</a> to specify a
transport-specific override, where <i>transport</i> is the <a href="master.5.html">master.cf</a>
name of the message delivery transport.
</p>


</DD>

<DT><b><a name="default_extra_recipient_limit">default_extra_recipient_limit</a>
(default: 1000)</b></DT><DD>

<p>
The default value for the extra per-transport limit imposed on the
number of in-memory recipients.  This extra recipient space is
reserved for the cases when the Postfix queue manager's scheduler
preempts one message with another and suddenly needs some extra
recipients slots for the chosen message in order to avoid performance
degradation.
</p>

<p> Use <a href="postconf.5.html#transport_extra_recipient_limit"><i>transport</i>_extra_recipient_limit</a> to specify a
transport-specific override, where <i>transport</i> is the <a href="master.5.html">master.cf</a>
name of the message delivery transport.
</p>


</DD>

<DT><b><a name="default_minimum_delivery_slots">default_minimum_delivery_slots</a>
(default: 3)</b></DT><DD>

<p>
How many recipients a message must have in order to invoke the
Postfix queue manager's scheduling algorithm at all.  Messages
which would never accumulate at least this many delivery slots
(subject to slot cost parameter as well) are never preempted.
</p>

<p> Use <a href="postconf.5.html#transport_minimum_delivery_slots"><i>transport</i>_minimum_delivery_slots</a> to specify a
transport-specific override, where <i>transport</i> is the <a href="master.5.html">master.cf</a>
name of the message delivery transport.
</p>


</DD>

<DT><b><a name="default_privs">default_privs</a>
(default: nobody)</b></DT><DD>

<p>
The default rights used by the <a href="local.8.html">local(8)</a> delivery agent for delivery
to external file or command.  These rights are used when delivery
is requested from an <a href="aliases.5.html">aliases(5)</a> file that is owned by <b>root</b>, or
when delivery is done on behalf of <b>root</b>. <b>DO NOT SPECIFY A
PRIVILEGED USER OR THE POSTFIX OWNER</b>.
</p>


</DD>

<DT><b><a name="default_process_limit">default_process_limit</a>
(default: 100)</b></DT><DD>

<p>
The default maximal number of Postfix child processes that provide
a given service. This limit can be overruled for specific services
in the <a href="master.5.html">master.cf</a> file.
</p>


</DD>

<DT><b><a name="default_rbl_reply">default_rbl_reply</a>
(default: see "postconf -d" output)</b></DT><DD>

<p>
The default SMTP server response template for a request that is
rejected by an RBL-based restriction. This template can be overruled
by specific entries in the optional <a href="postconf.5.html#rbl_reply_maps">rbl_reply_maps</a> lookup table.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>

<p>
The template is subject to exactly one level of $name substitution:
</p>

<dl>

<dt><b>$client</b></dt>

<dd>The client hostname and IP address, formatted as name[address]. </dd>

<dt><b>$client_address</b></dt>

<dd>The client IP address. </dd>

<dt><b>$client_name</b></dt>

<dd>The client hostname or "unknown". See <a href="postconf.5.html#reject_unknown_client_hostname">reject_unknown_client_hostname</a>
for more details. </dd>

<dt><b>$reverse_client_name</b></dt>

<dd>The client hostname from address-&gt;name lookup, or "unknown".
See <a href="postconf.5.html#reject_unknown_reverse_client_hostname">reject_unknown_reverse_client_hostname</a> for more details. </dd>

<dt><b>$helo_name</b></dt>

<dd>The hostname given in HELO or EHLO command or empty string. </dd>

<dt><b>$rbl_class</b></dt>

<dd>The blacklisted entity type: Client host, Helo command, Sender
address, or Recipient address. </dd>

<dt><b>$rbl_code</b></dt>

<dd>The numerical SMTP response code, as specified with the
<a href="postconf.5.html#maps_rbl_reject_code">maps_rbl_reject_code</a> configuration parameter. Note: The numerical
SMTP response code is required, and must appear at the start of the
reply. With Postfix version 2.3 and later this information may be followed
by an <a href="http://tools.ietf.org/html/rfc3463">RFC 3463</a> enhanced status code. </dd>

<dt><b>$rbl_domain</b></dt>

<dd>The RBL domain where $rbl_what is blacklisted. </dd>

<dt><b>$rbl_reason</b></dt>

<dd>The reason why $rbl_what is blacklisted, or an empty string. </dd>

<dt><b>$rbl_what</b></dt>

<dd>The entity that is blacklisted (an IP address, a hostname, a domain
name, or an email address whose domain was blacklisted). </dd>

<dt><b>$recipient</b></dt>

<dd>The recipient address or &lt;&gt; in case of the null address. </dd>

<dt><b>$recipient_domain</b></dt>

<dd>The recipient domain or empty string. </dd>

<dt><b>$recipient_name</b></dt>

<dd>The recipient address localpart or &lt;&gt; in case of null address. </dd>

<dt><b>$sender</b></dt>

<dd>The sender address or &lt;&gt; in case of the null address. </dd>

<dt><b>$sender_domain</b></dt>

<dd>The sender domain or empty string. </dd>

<dt><b>$sender_name</b></dt>

<dd>The sender address localpart or &lt;&gt; in case of the null address. </dd>

<dt><b>${name?text}</b></dt>

<dd>Expands to `text' if $name is not empty. </dd>

<dt><b>${name:text}</b></dt>

<dd>Expands to `text' if $name is empty. </dd>

</dl>

<p>
Instead of $name you can also specify ${name} or $(name).
</p>

<p> Note: when an enhanced status code is specified in an RBL reply
template, it is subject to modification.  The following transformations
are needed when the same RBL reply template is used for client,
helo, sender, or recipient access restrictions.  </p>

<ul>

<li> <p> When rejecting a sender address, the Postfix SMTP server
will transform a recipient DSN status (e.g., 4.1.1-4.1.6) into the
corresponding sender DSN status, and vice versa. </p>

<li> <p> When rejecting non-address information (such as the HELO
command argument or the client hostname/address), the Postfix SMTP
server will transform a sender or recipient DSN status into a generic
non-address DSN status (e.g., 4.0.0).  </p>

</ul>


</DD>

<DT><b><a name="default_recipient_limit">default_recipient_limit</a>
(default: 20000)</b></DT><DD>

<p>
The default per-transport upper limit on the number of in-memory
recipients.  These limits take priority over the global
<a href="postconf.5.html#qmgr_message_recipient_limit">qmgr_message_recipient_limit</a> after the message has been assigned
to the respective transports.  See also <a href="postconf.5.html#default_extra_recipient_limit">default_extra_recipient_limit</a>
and <a href="postconf.5.html#qmgr_message_recipient_minimum">qmgr_message_recipient_minimum</a>.
</p>

<p> Use <a href="postconf.5.html#transport_recipient_limit"><i>transport</i>_recipient_limit</a> to specify a
transport-specific override, where <i>transport</i> is the <a href="master.5.html">master.cf</a>
name of the message delivery transport.
</p>


</DD>

<DT><b><a name="default_recipient_refill_delay">default_recipient_refill_delay</a>
(default: 5s)</b></DT><DD>

<p>
The default per-transport maximum delay between recipients refills.
When not all message recipients fit into the memory at once, keep loading
more of them at least once every this many seconds.  This is used to
make sure the recipients are refilled in timely manner even when
$<a href="postconf.5.html#default_recipient_refill_limit">default_recipient_refill_limit</a> is too high for too slow deliveries.
</p>

<p> Use <a href="postconf.5.html#transport_recipient_refill_delay"><i>transport</i>_recipient_refill_delay</a> to specify a
transport-specific override, where <i>transport</i> is the <a href="master.5.html">master.cf</a>
name of the message delivery transport.
</p>

<p> This feature is available in Postfix 2.4 and later. </p>


</DD>

<DT><b><a name="default_recipient_refill_limit">default_recipient_refill_limit</a>
(default: 100)</b></DT><DD>

<p>
The default per-transport limit on the number of recipients refilled at
once.  When not all message recipients fit into the memory at once, keep
loading more of them in batches of at least this many at a time.  See also
$<a href="postconf.5.html#default_recipient_refill_delay">default_recipient_refill_delay</a>, which may result in recipient batches
lower than this when this limit is too high for too slow deliveries.
</p>

<p> Use <a href="postconf.5.html#transport_recipient_refill_limit"><i>transport</i>_recipient_refill_limit</a> to specify a
transport-specific override, where <i>transport</i> is the <a href="master.5.html">master.cf</a>
name of the message delivery transport.
</p>

<p> This feature is available in Postfix 2.4 and later. </p>


</DD>

<DT><b><a name="default_transport">default_transport</a>
(default: smtp)</b></DT><DD>

<p>
The default mail delivery transport and next-hop destination for
destinations that do not match $<a href="postconf.5.html#mydestination">mydestination</a>, $<a href="postconf.5.html#inet_interfaces">inet_interfaces</a>,
$<a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a>, $<a href="postconf.5.html#virtual_alias_domains">virtual_alias_domains</a>, $<a href="postconf.5.html#virtual_mailbox_domains">virtual_mailbox_domains</a>,
or $<a href="postconf.5.html#relay_domains">relay_domains</a>.  In order of decreasing precedence, the nexthop
destination is taken from $<a href="postconf.5.html#default_transport">default_transport</a>,
$<a href="postconf.5.html#sender_dependent_relayhost_maps">sender_dependent_relayhost_maps</a>, $<a href="postconf.5.html#relayhost">relayhost</a>, or from the recipient
domain. This information can be overruled with the <a href="transport.5.html">transport(5)</a>
table.
</p>

<p>
Specify a string of the form <i>transport:nexthop</i>, where <i>transport</i>
is the name of a mail delivery transport defined in <a href="master.5.html">master.cf</a>.
The <i>:nexthop</i> part is optional.  For more details see the
<a href="transport.5.html">transport(5)</a> manual page.
</p>

<p>
Example:
</p>

<pre>
<a href="postconf.5.html#default_transport">default_transport</a> = uucp:relayhostname
</pre>


</DD>

<DT><b><a name="default_verp_delimiters">default_verp_delimiters</a>
(default: +=)</b></DT><DD>

<p> The two default VERP delimiter characters. These are used when
no explicit delimiters are specified with the SMTP XVERP command
or with the "<b>sendmail -V</b>" command-line option. Specify
characters that are allowed by the <a href="postconf.5.html#verp_delimiter_filter">verp_delimiter_filter</a> setting.
</p>

<p>
This feature is available in Postfix 1.1 and later.
</p>


</DD>

<DT><b><a name="defer_code">defer_code</a>
(default: 450)</b></DT><DD>

<p>
The numerical Postfix SMTP server response code when a remote SMTP
client request is rejected by the "defer" restriction.
</p>

<p>
Do not change this unless you have a complete understanding of <a href="http://tools.ietf.org/html/rfc821">RFC 821</a>.
</p>


</DD>

<DT><b><a name="defer_service_name">defer_service_name</a>
(default: defer)</b></DT><DD>

<p>
The name of the defer service. This service is implemented by the
<a href="bounce.8.html">bounce(8)</a> daemon and maintains a record
of failed delivery attempts and generates non-delivery notifications.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>


</DD>

<DT><b><a name="defer_transports">defer_transports</a>
(default: empty)</b></DT><DD>

<p>
The names of message delivery transports that should not deliver mail
unless someone issues "<b>sendmail -q</b>" or equivalent. Specify zero
or more names of mail delivery transports names that appear in the
first field of <a href="master.5.html">master.cf</a>.
</p>

<p>
Example:
</p>

<pre>
<a href="postconf.5.html#defer_transports">defer_transports</a> = smtp
</pre>


</DD>

<DT><b><a name="delay_logging_resolution_limit">delay_logging_resolution_limit</a>
(default: 2)</b></DT><DD>

<p> The maximal number of digits after the decimal point when logging
sub-second delay values.  Specify a number in the range 0..6.  </p>

<p> Large delay values are rounded off to an integral number seconds;
delay values below the <a href="postconf.5.html#delay_logging_resolution_limit">delay_logging_resolution_limit</a> are logged
as "0", and small delay values are logged with at most two-digit
precision.  </p>

<p> The format of the "delays=a/b/c/d" logging is as follows: </p>

<ul>

<li> a = time from message arrival to last <a href="QSHAPE_README.html#active_queue">active queue</a> entry

<li> b = time from last <a href="QSHAPE_README.html#active_queue">active queue</a> entry to connection setup

<li> c = time in connection setup, including DNS, EHLO and TLS

<li> d = time in message transmission

</ul>

<p> This feature is available in Postfix 2.3 and later.  </p>


</DD>

<DT><b><a name="delay_notice_recipient">delay_notice_recipient</a>
(default: postmaster)</b></DT><DD>

<p>
The recipient of postmaster notifications with the message headers
of mail that cannot be delivered within $<a href="postconf.5.html#delay_warning_time">delay_warning_time</a> time
units.  </p>

<p>
This feature is enabled with the <a href="postconf.5.html#delay_warning_time">delay_warning_time</a> parameter.
</p>


</DD>

<DT><b><a name="delay_warning_time">delay_warning_time</a>
(default: 0h)</b></DT><DD>

<p>
The time after which the sender receives the message headers of
mail that is still queued.
</p>

<p>
To enable this feature, specify a non-zero time value (an integral
value plus an optional one-letter suffix that specifies the time
unit).
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is h (hours).
</p>


</DD>

<DT><b><a name="deliver_lock_attempts">deliver_lock_attempts</a>
(default: 20)</b></DT><DD>

<p>
The maximal number of attempts to acquire an exclusive lock on a
mailbox file or <a href="bounce.8.html">bounce(8)</a> logfile.
</p>


</DD>

<DT><b><a name="deliver_lock_delay">deliver_lock_delay</a>
(default: 1s)</b></DT><DD>

<p>
The time between attempts to acquire an exclusive lock on a mailbox
file or <a href="bounce.8.html">bounce(8)</a> logfile.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>


</DD>

<DT><b><a name="destination_concurrency_feedback_debug">destination_concurrency_feedback_debug</a>
(default: no)</b></DT><DD>

<p> Make the queue manager's feedback algorithm verbose for performance
analysis purposes. </p>

<p> This feature is available in Postfix 2.5 and later. </p>


</DD>

<DT><b><a name="detect_8bit_encoding_header">detect_8bit_encoding_header</a>
(default: yes)</b></DT><DD>

<p> Automatically detect 8BITMIME body content by looking at
Content-Transfer-Encoding: message headers; historically, this
behavior was hard-coded to be "always on".  </p>

<p> This feature is available in Postfix 2.5 and later. </p>


</DD>

<DT><b><a name="disable_dns_lookups">disable_dns_lookups</a>
(default: no)</b></DT><DD>

<p>
Disable DNS lookups in the Postfix SMTP and LMTP clients. When
disabled, hosts are looked up with the getaddrinfo() system
library routine which normally also looks in /etc/hosts.
</p>

<p>
DNS lookups are enabled by default.
</p>


</DD>

<DT><b><a name="disable_mime_input_processing">disable_mime_input_processing</a>
(default: no)</b></DT><DD>

<p>
Turn off MIME processing while receiving mail. This means that no
special treatment is given to Content-Type: message headers, and
that all text after the initial message headers is considered to
be part of the message body.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>

<p>
Mime input processing is enabled by default, and is needed in order
to recognize MIME headers in message content.
</p>


</DD>

<DT><b><a name="disable_mime_output_conversion">disable_mime_output_conversion</a>
(default: no)</b></DT><DD>

<p>
Disable the conversion of 8BITMIME format to 7BIT format.  Mime
output conversion is needed when the destination does not advertise
8BITMIME support.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>


</DD>

<DT><b><a name="disable_verp_bounces">disable_verp_bounces</a>
(default: no)</b></DT><DD>

<p>
Disable sending one bounce report per recipient.
</p>

<p>
The default, one per recipient, is what ezmlm needs.
</p>

<p>
This feature is available in Postfix 1.1 and later.
</p>


</DD>

<DT><b><a name="disable_vrfy_command">disable_vrfy_command</a>
(default: no)</b></DT><DD>

<p>
Disable the SMTP VRFY command. This stops some techniques used to
harvest email addresses.
</p>

<p>
Example:
</p>

<pre>
<a href="postconf.5.html#disable_vrfy_command">disable_vrfy_command</a> = no
</pre>


</DD>

<DT><b><a name="dont_remove">dont_remove</a>
(default: 0)</b></DT><DD>

<p>
Don't remove queue files and save them to the "saved" mail queue.
This is a debugging aid.  To inspect the envelope information and
content of a Postfix queue file, use the <a href="postcat.1.html">postcat(1)</a> command.
</p>


</DD>

<DT><b><a name="double_bounce_sender">double_bounce_sender</a>
(default: double-bounce)</b></DT><DD>

<p> The sender address of postmaster notifications that are generated
by the mail system. All mail to this address is silently discarded,
in order to terminate mail bounce loops.  </p>


</DD>

<DT><b><a name="duplicate_filter_limit">duplicate_filter_limit</a>
(default: 1000)</b></DT><DD>

<p> The maximal number of addresses remembered by the address
duplicate filter for <a href="aliases.5.html">aliases(5)</a> or <a href="virtual.5.html">virtual(5)</a> alias expansion, or
for <a href="showq.8.html">showq(8)</a> queue displays.  </p>


</DD>

<DT><b><a name="empty_address_recipient">empty_address_recipient</a>
(default: MAILER-DAEMON)</b></DT><DD>

<p>
The recipient of mail addressed to the null address.  Postfix does
not accept such addresses in SMTP commands, but they may still be
created locally as the result of configuration or software error.
</p>


</DD>

<DT><b><a name="empty_address_relayhost_maps_lookup_key">empty_address_relayhost_maps_lookup_key</a>
(default: &lt;&gt;)</b></DT><DD>

<p> The <a href="postconf.5.html#sender_dependent_relayhost_maps">sender_dependent_relayhost_maps</a> search string that will be
used instead of the null sender address. </p>

<p> This feature is available in Postfix 2.5 and later. With
earlier versions, <a href="postconf.5.html#sender_dependent_relayhost_maps">sender_dependent_relayhost_maps</a> lookups were
skipped for the null sender address.  </p>


</DD>

<DT><b><a name="enable_errors_to">enable_errors_to</a>
(default: no)</b></DT><DD>

<p> Report mail delivery errors to the address specified with the
non-standard Errors-To: message header, instead of the envelope
sender address (this feature is removed with Postfix version 2.2, is
turned off by default with Postfix version 2.1, and is always turned on
with older Postfix versions).  </p>


</DD>

<DT><b><a name="enable_original_recipient">enable_original_recipient</a>
(default: yes)</b></DT><DD>

<p> Enable support for the X-Original-To message header. This header
is needed for multi-recipient mailboxes.  </p>

<p> When this parameter is set to yes, the <a href="cleanup.8.html">cleanup(8)</a> daemon performs
duplicate elimination on distinct pairs of (original recipient,
rewritten recipient), and generates non-empty original recipient
queue file records.  </p>

<p> When this parameter is set to no, the <a href="cleanup.8.html">cleanup(8)</a> daemon performs
duplicate elimination on the rewritten recipient address only, and
generates empty original recipient queue file records.  </p>

<p> This feature is available in Postfix 2.1 and later. With Postfix
version 2.0, support for the X-Original-To message header is always turned
on. Postfix versions before 2.0 have no support for the X-Original-To
message header.  </p>


</DD>

<DT><b><a name="error_notice_recipient">error_notice_recipient</a>
(default: postmaster)</b></DT><DD>

<p> The recipient of postmaster notifications about mail delivery
problems that are caused by policy, resource, software or protocol
errors.  These notifications are enabled with the <a href="postconf.5.html#notify_classes">notify_classes</a>
parameter.  </p>


</DD>

<DT><b><a name="error_service_name">error_service_name</a>
(default: error)</b></DT><DD>

<p>
The name of the <a href="error.8.html">error(8)</a> pseudo delivery agent. This service always
returns mail as undeliverable.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>


</DD>

<DT><b><a name="execution_directory_expansion_filter">execution_directory_expansion_filter</a>
(default: see "postconf -d" output)</b></DT><DD>

<p> Restrict the characters that the <a href="local.8.html">local(8)</a> delivery agent allows
in $name expansions of $<a href="postconf.5.html#command_execution_directory">command_execution_directory</a>.  Characters
outside the allowed set are replaced by underscores.  </p>

<p> This feature is available in Postfix 2.2 and later. </p>


</DD>

<DT><b><a name="expand_owner_alias">expand_owner_alias</a>
(default: no)</b></DT><DD>

<p>
When delivering to an alias "aliasname" that has an "owner-aliasname"
companion alias, set the envelope sender address to the expansion
of the "owner-aliasname" alias. Normally, Postfix sets the envelope
sender address to the name of the "owner-aliasname" alias.
</p>


</DD>

<DT><b><a name="export_environment">export_environment</a>
(default: see "postconf -d" output)</b></DT><DD>

<p>
The list of environment variables that a Postfix process will export
to non-Postfix processes. The TZ variable is needed for sane
time keeping on System-V-ish systems.
</p>

<p>
Specify a list of names and/or name=value pairs, separated by
whitespace or comma. The name=value form is supported with
Postfix version 2.1 and later.
</p>

<p>
Example:
</p>

<pre>
<a href="postconf.5.html#export_environment">export_environment</a> = TZ PATH=/bin:/usr/bin
</pre>


</DD>

<DT><b><a name="extract_recipient_limit">extract_recipient_limit</a>
(default: 10240)</b></DT><DD>

<p>
The maximal number of recipient addresses that Postfix will extract
from message headers when mail is submitted with "<b>sendmail -t</b>".
</p>

<p>
This feature was removed in Postfix version 2.1.
</p>


</DD>

<DT><b><a name="fallback_relay">fallback_relay</a>
(default: empty)</b></DT><DD>

<p>
Optional list of relay hosts for SMTP destinations that can't be
found or that are unreachable. With Postfix 2.3 this parameter
is renamed to <a href="postconf.5.html#smtp_fallback_relay">smtp_fallback_relay</a>. </p>

<p>
By default, mail is returned to the sender when a destination is
not found, and delivery is deferred when a destination is unreachable.
</p>

<p> The fallback relays must be SMTP destinations. Specify a domain,
host, host:port, [host]:port, [address] or [address]:port; the form
[host] turns off MX lookups.  If you specify multiple SMTP
destinations, Postfix will try them in the specified order.  </p>

<p> Note: before Postfix 2.2, do not use the <a href="postconf.5.html#fallback_relay">fallback_relay</a> feature
when relaying mail
for a backup or primary MX domain. Mail would loop between the
Postfix MX host and the <a href="postconf.5.html#fallback_relay">fallback_relay</a> host when the final destination
is unavailable. </p>

<ul>

<li> In <a href="postconf.5.html">main.cf</a> specify "<a href="postconf.5.html#relay_transport">relay_transport</a> = relay",

<li> In <a href="master.5.html">master.cf</a> specify "-o <a href="postconf.5.html#fallback_relay">fallback_relay</a> =" (i.e., empty) at
the end of the <tt>relay</tt> entry.

<li> In transport maps, specify "relay:<i>nexthop...</i>"
as the right-hand side for backup or primary MX domain entries.

</ul>

<p> Postfix version 2.2 and later will not use the <a href="postconf.5.html#fallback_relay">fallback_relay</a> feature
for destinations that it is MX host for.
</p>


</DD>

<DT><b><a name="fallback_transport">fallback_transport</a>
(default: empty)</b></DT><DD>

<p>
Optional message delivery transport that the <a href="local.8.html">local(8)</a> delivery
agent should use for names that are not found in the <a href="aliases.5.html">aliases(5)</a>
or UNIX password database.
</p>

<p> The precedence of <a href="local.8.html">local(8)</a> delivery features from high to low
is: aliases, .forward files, <a href="postconf.5.html#mailbox_transport_maps">mailbox_transport_maps</a>, <a href="postconf.5.html#mailbox_transport">mailbox_transport</a>,
<a href="postconf.5.html#mailbox_command_maps">mailbox_command_maps</a>, <a href="postconf.5.html#mailbox_command">mailbox_command</a>, <a href="postconf.5.html#home_mailbox">home_mailbox</a>, <a href="postconf.5.html#mail_spool_directory">mail_spool_directory</a>,
<a href="postconf.5.html#fallback_transport_maps">fallback_transport_maps</a>, <a href="postconf.5.html#fallback_transport">fallback_transport</a> and <a href="postconf.5.html#luser_relay">luser_relay</a>.  </p>


</DD>

<DT><b><a name="fallback_transport_maps">fallback_transport_maps</a>
(default: empty)</b></DT><DD>

<p> Optional lookup tables with per-recipient message delivery
transports for recipients that the <a href="local.8.html">local(8)</a> delivery agent could
not find in the <a href="aliases.5.html">aliases(5)</a> or UNIX password database. </p>

<p> The precedence of <a href="local.8.html">local(8)</a> delivery features from high to low
is: aliases, .forward files, <a href="postconf.5.html#mailbox_transport_maps">mailbox_transport_maps</a>, <a href="postconf.5.html#mailbox_transport">mailbox_transport</a>,
<a href="postconf.5.html#mailbox_command_maps">mailbox_command_maps</a>, <a href="postconf.5.html#mailbox_command">mailbox_command</a>, <a href="postconf.5.html#home_mailbox">home_mailbox</a>, <a href="postconf.5.html#mail_spool_directory">mail_spool_directory</a>,
<a href="postconf.5.html#fallback_transport_maps">fallback_transport_maps</a>, <a href="postconf.5.html#fallback_transport">fallback_transport</a> and <a href="postconf.5.html#luser_relay">luser_relay</a>.  </p>

<p> For safety reasons, this feature does not allow $number
substitutions in regular expression maps. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="fast_flush_domains">fast_flush_domains</a>
(default: $<a href="postconf.5.html#relay_domains">relay_domains</a>)</b></DT><DD>

<p>
Optional list of destinations that are eligible for per-destination
logfiles with mail that is queued to those destinations.
</p>

<p>
By default, Postfix maintains "fast flush" logfiles only for
destinations that the Postfix SMTP server is willing to relay to
(i.e. the default is: "<a href="postconf.5.html#fast_flush_domains">fast_flush_domains</a> = $<a href="postconf.5.html#relay_domains">relay_domains</a>"; see
the <a href="postconf.5.html#relay_domains">relay_domains</a> parameter in the <a href="postconf.5.html">postconf(5)</a> manual).
</p>

<p> Specify a list of hosts or domains, "/file/name" patterns or
"<a href="DATABASE_README.html">type:table</a>" lookup tables, separated by commas and/or whitespace.
Continue long lines by starting the next line with whitespace. A
"/file/name" pattern is replaced by its contents; a "<a href="DATABASE_README.html">type:table</a>"
lookup table is matched when the domain or its parent domain appears
as lookup key.  </p>

<p>
Specify "<a href="postconf.5.html#fast_flush_domains">fast_flush_domains</a> =" (i.e., empty) to disable the feature
altogether.
</p>


</DD>

<DT><b><a name="fast_flush_purge_time">fast_flush_purge_time</a>
(default: 7d)</b></DT><DD>

<p>
The time after which an empty per-destination "fast flush" logfile
is deleted.
</p>

<p>
You can specify the time as a number, or as a number followed by
a letter that indicates the time unit: s=seconds, m=minutes, h=hours,
d=days, w=weeks.  The default time unit is days.
</p>


</DD>

<DT><b><a name="fast_flush_refresh_time">fast_flush_refresh_time</a>
(default: 12h)</b></DT><DD>

<p>
The time after which a non-empty but unread per-destination "fast
flush" logfile needs to be refreshed.  The contents of a logfile
are refreshed by requesting delivery of all messages listed in the
logfile.
</p>

<p>
You can specify the time as a number, or as a number followed by
a letter that indicates the time unit: s=seconds, m=minutes, h=hours,
d=days, w=weeks.  The default time unit is hours.
</p>


</DD>

<DT><b><a name="fault_injection_code">fault_injection_code</a>
(default: 0)</b></DT><DD>

<p>
Force specific internal tests to fail, to test the handling of
errors that are difficult to reproduce otherwise.
</p>


</DD>

<DT><b><a name="flush_service_name">flush_service_name</a>
(default: flush)</b></DT><DD>

<p>
The name of the <a href="flush.8.html">flush(8)</a> service. This service maintains per-destination
logfiles with the queue file names of mail that is queued for those
destinations.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>


</DD>

<DT><b><a name="fork_attempts">fork_attempts</a>
(default: 5)</b></DT><DD>

<p> The maximal number of attempts to fork() a child process.  </p>


</DD>

<DT><b><a name="fork_delay">fork_delay</a>
(default: 1s)</b></DT><DD>

<p> The delay between attempts to fork() a child process.  </p>

<p> Time units: s (seconds), m (minutes), h (hours), d (days), w
(weeks).  The default time unit is s (seconds).  </p>


</DD>

<DT><b><a name="forward_expansion_filter">forward_expansion_filter</a>
(default: see "postconf -d" output)</b></DT><DD>

<p>
Restrict the characters that the <a href="local.8.html">local(8)</a> delivery agent allows in
$name expansions of $<a href="postconf.5.html#forward_path">forward_path</a>.  Characters outside the
allowed set are replaced by underscores.
</p>


</DD>

<DT><b><a name="forward_path">forward_path</a>
(default: see "postconf -d" output)</b></DT><DD>

<p> The <a href="local.8.html">local(8)</a> delivery agent search list for finding a .forward
file with user-specified delivery methods. The first file that is
found is used.  </p>

<p> The following $name expansions are done on <a href="postconf.5.html#forward_path">forward_path</a> before
the search actually happens. The result of $name expansion is
filtered with the character set that is specified with the
<a href="postconf.5.html#forward_expansion_filter">forward_expansion_filter</a> parameter.  </p>

<dl>

<dt><b>$user</b></dt>

<dd>The recipient's username. </dd>

<dt><b>$shell</b></dt>

<dd>The recipient's login shell pathname. </dd>

<dt><b>$home</b></dt>

<dd>The recipient's home directory. </dd>

<dt><b>$recipient</b></dt>

<dd>The full recipient address. </dd>

<dt><b>$extension</b></dt>

<dd>The optional recipient address extension. </dd>

<dt><b>$domain</b></dt>

<dd>The recipient domain. </dd>

<dt><b>$local</b></dt>

<dd>The entire recipient localpart. </dd>

<dt><b>$<a href="postconf.5.html#recipient_delimiter">recipient_delimiter</a></b></dt>

<dd>The system-wide recipient address extension delimiter. </dd>

<dt><b>${name?value}</b></dt>

<dd>Expands to <i>value</i> when <i>$name</i> is non-empty. </dd>

<dt><b>${name:value}</b></dt>

<dd>Expands to <i>value</i> when <i>$name</i> is empty. </dd>

</dl>

<p>
Instead of $name you can also specify ${name} or $(name).
</p>

<p>
Examples:
</p>

<pre>
<a href="postconf.5.html#forward_path">forward_path</a> = /var/forward/$user
<a href="postconf.5.html#forward_path">forward_path</a> =
    /var/forward/$user/.forward$<a href="postconf.5.html#recipient_delimiter">recipient_delimiter</a>$extension,
    /var/forward/$user/.forward
</pre>


</DD>

<DT><b><a name="frozen_delivered_to">frozen_delivered_to</a>
(default: yes)</b></DT><DD>

<p> Update the <a href="local.8.html">local(8)</a> delivery agent's idea of the Delivered-To:
address (see <a href="postconf.5.html#prepend_delivered_header">prepend_delivered_header</a>) only once, at the start of
a delivery attempt; do not update the Delivered-To: address while
expanding aliases or .forward files. </p>

<p> This feature is available in Postfix 2.3 and later. With older
Postfix releases, the behavior is as if this parameter is set to
"no". The old setting can be expensive with deeply nested aliases
or .forward files. When an alias or .forward file changes the
Delivered-To: address, it ties up one queue file and one cleanup
process instance while mail is being forwarded.  </p>


</DD>

<DT><b><a name="hash_queue_depth">hash_queue_depth</a>
(default: 1)</b></DT><DD>

<p>
The number of subdirectory levels for queue directories listed with
the <a href="postconf.5.html#hash_queue_names">hash_queue_names</a> parameter.
</p>

<p>
After changing the <a href="postconf.5.html#hash_queue_names">hash_queue_names</a> or <a href="postconf.5.html#hash_queue_depth">hash_queue_depth</a> parameter,
execute the command "<b>postfix reload</b>".
</p>


</DD>

<DT><b><a name="hash_queue_names">hash_queue_names</a>
(default: deferred, defer)</b></DT><DD>

<p>
The names of queue directories that are split across multiple
subdirectory levels.
</p>

<p> Before Postfix version 2.2, the default list of hashed queues
was significantly larger. Claims about improvements in file system
technology suggest that hashing of the <a href="QSHAPE_README.html#incoming_queue">incoming</a> and <a href="QSHAPE_README.html#active_queue">active queues</a>
is no longer needed. Fewer hashed directories speed up the time
needed to restart Postfix. </p>

<p>
After changing the <a href="postconf.5.html#hash_queue_names">hash_queue_names</a> or <a href="postconf.5.html#hash_queue_depth">hash_queue_depth</a> parameter,
execute the command "<b>postfix reload</b>".
</p>


</DD>

<DT><b><a name="header_address_token_limit">header_address_token_limit</a>
(default: 10240)</b></DT><DD>

<p>
The maximal number of address tokens are allowed in an address
message header. Information that exceeds the limit is discarded.
The limit is enforced by the <a href="cleanup.8.html">cleanup(8)</a> server.
</p>


</DD>

<DT><b><a name="header_checks">header_checks</a>
(default: empty)</b></DT><DD>

<p>
Optional lookup tables for content inspection of primary non-MIME
message headers, as specified in the <a href="header_checks.5.html">header_checks(5)</a> manual page.
</p>


</DD>

<DT><b><a name="header_size_limit">header_size_limit</a>
(default: 102400)</b></DT><DD>

<p>
The maximal amount of memory in bytes for storing a message header.
If a header is larger, the excess is discarded.  The limit is
enforced by the <a href="cleanup.8.html">cleanup(8)</a> server.
</p>


</DD>

<DT><b><a name="helpful_warnings">helpful_warnings</a>
(default: yes)</b></DT><DD>

<p>
Log warnings about problematic configuration settings, and provide
helpful suggestions.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>


</DD>

<DT><b><a name="home_mailbox">home_mailbox</a>
(default: empty)</b></DT><DD>

<p>
Optional pathname of a mailbox file relative to a <a href="local.8.html">local(8)</a> user's
home directory.
</p>

<p>
Specify a pathname ending in "/" for qmail-style delivery.
</p>

<p> The precedence of <a href="local.8.html">local(8)</a> delivery features from high to low
is: aliases, .forward files, <a href="postconf.5.html#mailbox_transport_maps">mailbox_transport_maps</a>, <a href="postconf.5.html#mailbox_transport">mailbox_transport</a>,
<a href="postconf.5.html#mailbox_command_maps">mailbox_command_maps</a>, <a href="postconf.5.html#mailbox_command">mailbox_command</a>, <a href="postconf.5.html#home_mailbox">home_mailbox</a>, <a href="postconf.5.html#mail_spool_directory">mail_spool_directory</a>,
<a href="postconf.5.html#fallback_transport_maps">fallback_transport_maps</a>, <a href="postconf.5.html#fallback_transport">fallback_transport</a> and <a href="postconf.5.html#luser_relay">luser_relay</a>.  </p>

<p>
Examples:
</p>

<pre>
<a href="postconf.5.html#home_mailbox">home_mailbox</a> = Mailbox
<a href="postconf.5.html#home_mailbox">home_mailbox</a> = Maildir/
</pre>


</DD>

<DT><b><a name="hopcount_limit">hopcount_limit</a>
(default: 50)</b></DT><DD>

<p>
The maximal number of Received:  message headers that is allowed
in the primary message headers. A message that exceeds the limit
is bounced, in order to stop a mailer loop.
</p>


</DD>

<DT><b><a name="html_directory">html_directory</a>
(default: see "postconf -d" output)</b></DT><DD>

<p>
The location of Postfix HTML files that describe how to build,
configure or operate a specific Postfix subsystem or feature.
</p>


</DD>

<DT><b><a name="ignore_mx_lookup_error">ignore_mx_lookup_error</a>
(default: no)</b></DT><DD>

<p> Ignore DNS MX lookups that produce no response.  By default,
the Postfix SMTP client defers delivery and tries again after some
delay.  This behavior is required by the SMTP standard.  </p>

<p>
Specify "<a href="postconf.5.html#ignore_mx_lookup_error">ignore_mx_lookup_error</a> = yes" to force a DNS A record
lookup instead. This violates the SMTP standard and can result in
mis-delivery of mail.
</p>


</DD>

<DT><b><a name="import_environment">import_environment</a>
(default: see "postconf -d" output)</b></DT><DD>

<p>
The list of environment parameters that a Postfix process will
import from a non-Postfix parent process. Examples of relevant
parameters:
</p>

<dl>

<dt><b>TZ</b></dt>

<dd>Needed for sane time keeping on most System-V-ish systems. </dd>

<dt><b>DISPLAY</b></dt>

<dd>Needed for debugging Postfix daemons with an X-windows debugger. </dd>

<dt><b>XAUTHORITY</b></dt>

<dd>Needed for debugging Postfix daemons with an X-windows debugger. </dd>

<dt><b>MAIL_CONFIG</b></dt>

<dd>Needed to make "<b>postfix -c</b>" work. </dd>

</dl>

<p> Specify a list of names and/or name=value pairs, separated by
whitespace or comma. The name=value form is supported with
Postfix version 2.1 and later.  </p>


</DD>

<DT><b><a name="in_flow_delay">in_flow_delay</a>
(default: 1s)</b></DT><DD>

<p> Time to pause before accepting a new message, when the message
arrival rate exceeds the message delivery rate. This feature is
turned on by default (it's disabled on SCO UNIX due to an SCO bug).
</p>

<p>
With the default 100 SMTP server process limit, "<a href="postconf.5.html#in_flow_delay">in_flow_delay</a>
= 1s" limits the mail inflow to 100 messages per second above the
number of messages delivered per second.
</p>

<p>
Specify 0 to disable the feature. Valid delays are 0..10.
</p>


</DD>

<DT><b><a name="inet_interfaces">inet_interfaces</a>
(default: all)</b></DT><DD>

<p> The network interface addresses that this mail system receives
mail on. Specify "all" to receive mail on all network
interfaces (default), and "loopback-only" to receive mail
on loopback network interfaces only (Postfix version 2.2 and later).  The
parameter also controls delivery of mail to <tt>user@[ip.address]</tt>.
</p>

<p>
Note 1: you need to stop and start Postfix when this parameter changes.
</p>

<p> Note 2: address information may be enclosed inside <tt>[]</tt>,
but this form is not required here. </p>

<p> When <a href="postconf.5.html#inet_interfaces">inet_interfaces</a> specifies just one IPv4 and/or IPv6 address
that is not a loopback address, the Postfix SMTP client will use
this address as the IP source address for outbound mail. Support
for IPv6 is available in Postfix version 2.2 and later. </p>

<p>
On a multi-homed firewall with separate Postfix instances listening on the
"inside" and "outside" interfaces, this can prevent each instance from
being able to reach servers on the "other side" of the firewall. Setting
<a href="postconf.5.html#smtp_bind_address">smtp_bind_address</a> to 0.0.0.0 avoids the potential problem for
IPv4, and setting <a href="postconf.5.html#smtp_bind_address6">smtp_bind_address6</a> to :: solves the problem
for IPv6. </p>

<p>
A better solution for multi-homed firewalls is to leave <a href="postconf.5.html#inet_interfaces">inet_interfaces</a>
at the default value and instead use explicit IP addresses in
the <a href="master.5.html">master.cf</a> SMTP server definitions.  This preserves the Postfix
SMTP client's
loop detection, by ensuring that each side of the firewall knows that the
other IP address is still the same host. Setting $<a href="postconf.5.html#inet_interfaces">inet_interfaces</a> to a
single IPv4 and/or IPV6 address is primarily useful with virtual
hosting of domains on
secondary IP addresses, when each IP address serves a different domain
(and has a different $<a href="postconf.5.html#myhostname">myhostname</a> setting). </p>

<p>
See also the <a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a> parameter, for network addresses that
are forwarded to Postfix by way of a proxy or address translator.
</p>

<p>
Examples:
</p>

<pre>
<a href="postconf.5.html#inet_interfaces">inet_interfaces</a> = all (DEFAULT)
<a href="postconf.5.html#inet_interfaces">inet_interfaces</a> = loopback-only (Postfix version 2.2 and later)
<a href="postconf.5.html#inet_interfaces">inet_interfaces</a> = 127.0.0.1
<a href="postconf.5.html#inet_interfaces">inet_interfaces</a> = 127.0.0.1, [::1] (Postfix version 2.2 and later)
<a href="postconf.5.html#inet_interfaces">inet_interfaces</a> = 192.168.1.2, 127.0.0.1
</pre>


</DD>

<DT><b><a name="inet_protocols">inet_protocols</a>
(default: ipv4)</b></DT><DD>

<p> The Internet protocols Postfix will attempt to use when making
or accepting connections. Specify one or more of "ipv4"
or "ipv6", separated by whitespace or commas. The form
"all" is equivalent to "ipv4, ipv6" or "ipv4", depending
on whether the operating system implements IPv6. </p>

<p> This feature is available in Postfix 2.2 and later. </p>

<p> Note: you MUST stop and start Postfix after changing this
parameter. </p>

<p> On systems that pre-date IPV6_V6ONLY support (<a href="http://tools.ietf.org/html/rfc3493">RFC 3493</a>), an
IPv6 server will also accept IPv4 connections, even when IPv4 is
turned off with the <a href="postconf.5.html#inet_protocols">inet_protocols</a> parameter.  On systems with
IPV6_V6ONLY support, Postfix will use separate server sockets for
IPv6 and IPv4, and each will accept only connections for the
corresponding protocol.  </p>

<p> When IPv4 support is enabled via the <a href="postconf.5.html#inet_protocols">inet_protocols</a> parameter,
Postfix will to DNS type A record lookups, and will convert
IPv4-in-IPv6 client IP addresses (::ffff:1.2.3.4) to their original
IPv4 form (1.2.3.4).  The latter is needed on hosts that pre-date
IPV6_V6ONLY support (<a href="http://tools.ietf.org/html/rfc3493">RFC 3493</a>). </p>

<p> When IPv6 support is enabled via the <a href="postconf.5.html#inet_protocols">inet_protocols</a> parameter,
Postfix will do DNS type AAAA record lookups. </p>

<p> When both IPv4 and IPv6 support are enabled, the Postfix SMTP
client will attempt to connect via IPv6 before attempting to use
IPv4.  </p>

<p>
Examples:
</p>

<pre>
<a href="postconf.5.html#inet_protocols">inet_protocols</a> = ipv4 (DEFAULT)
<a href="postconf.5.html#inet_protocols">inet_protocols</a> = all
<a href="postconf.5.html#inet_protocols">inet_protocols</a> = ipv6
<a href="postconf.5.html#inet_protocols">inet_protocols</a> = ipv4, ipv6
</pre>


</DD>

<DT><b><a name="initial_destination_concurrency">initial_destination_concurrency</a>
(default: 5)</b></DT><DD>

<p>
The initial per-destination concurrency level for parallel delivery
to the same destination.
With per-destination recipient limit &gt; 1, a destination is a domain,
otherwise it is a recipient.
</p>

<p> Use <a href="postconf.5.html#transport_initial_destination_concurrency"><i>transport</i>_initial_destination_concurrency</a> to specify
a transport-specific override, where <i>transport</i> is the <a href="master.5.html">master.cf</a>
name of the message delivery transport (Postfix 2.5 and later). </p>

<p>
Warning: with concurrency of 1, one bad message can be enough to
block all mail to a site.
</p>


</DD>

<DT><b><a name="internal_mail_filter_classes">internal_mail_filter_classes</a>
(default: empty)</b></DT><DD>

<p> What categories of Postfix-generated mail are subject to
before-queue content inspection by <a href="postconf.5.html#non_smtpd_milters">non_smtpd_milters</a>, <a href="postconf.5.html#header_checks">header_checks</a>
and <a href="postconf.5.html#body_checks">body_checks</a>.  Specify zero or more of the following, separated
by whitespace or comma.  </p>

<dl>

<dt><b>bounce</b></dt> <dd> Inspect the content of delivery
status notifications. </dd>

<dt><b>notify</b></dt> <dd> Inspect the content of postmaster
notifications by the <a href="smtp.8.html">smtp(8)</a> and <a href="smtpd.8.html">smtpd(8)</a> processes. </dd>

</dl>

<p> NOTE: It's generally not safe to enable content inspection of
Postfix-generated email messages. The user is warned. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="invalid_hostname_reject_code">invalid_hostname_reject_code</a>
(default: 501)</b></DT><DD>

<p>
The numerical Postfix SMTP server response code when the client
HELO or EHLO command parameter is rejected by the <a href="postconf.5.html#reject_invalid_helo_hostname">reject_invalid_helo_hostname</a>
restriction.
</p>

<p>
Do not change this unless you have a complete understanding of <a href="http://tools.ietf.org/html/rfc821">RFC 821</a>.
</p>


</DD>

<DT><b><a name="ipc_idle">ipc_idle</a>
(default: version dependent)</b></DT><DD>

<p>
The time after which a client closes an idle internal communication
channel.  The purpose is to allow servers to terminate voluntarily
after they become idle. This is used, for example, by the address
resolving and rewriting clients.
</p>

<p> With Postfix 2.4 the default value was reduced from 100s to 5s. </p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>


</DD>

<DT><b><a name="ipc_timeout">ipc_timeout</a>
(default: 3600s)</b></DT><DD>

<p>
The time limit for sending or receiving information over an internal
communication channel.  The purpose is to break out of deadlock
situations. If the time limit is exceeded the software aborts with a
fatal error.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>


</DD>

<DT><b><a name="ipc_ttl">ipc_ttl</a>
(default: 1000s)</b></DT><DD>

<p>
The time after which a client closes an active internal communication
channel.  The purpose is to allow servers to terminate voluntarily
after reaching their client limit.  This is used, for example, by
the address resolving and rewriting clients.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>


</DD>

<DT><b><a name="line_length_limit">line_length_limit</a>
(default: 2048)</b></DT><DD>

<p> Upon input, long lines are chopped up into pieces of at most
this length; upon delivery, long lines are reconstructed.  </p>


</DD>

<DT><b><a name="lmtp_bind_address">lmtp_bind_address</a>
(default: empty)</b></DT><DD>

<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_bind_address">smtp_bind_address</a> configuration
parameter.  See there for details. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="lmtp_bind_address6">lmtp_bind_address6</a>
(default: empty)</b></DT><DD>

<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_bind_address6">smtp_bind_address6</a> configuration
parameter.  See there for details. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="lmtp_cache_connection">lmtp_cache_connection</a>
(default: yes)</b></DT><DD>

<p>
Keep Postfix LMTP client connections open for up to $<a href="postconf.5.html#max_idle">max_idle</a>
seconds. When the LMTP client receives a request for the same
connection the connection is reused.
</p>

<p>
The effectiveness of cached connections will be determined by the
number of LMTP servers in use, and the concurrency limit specified
for the LMTP client. Cached connections are closed under any of
the following conditions:
</p>

<ul>

<li> The LMTP client idle time limit is reached.  This limit is
specified with the Postfix <a href="postconf.5.html#max_idle">max_idle</a> configuration parameter.

<li> A delivery request specifies a different destination than the
one currently cached.

<li> The per-process limit on the number of delivery requests is
reached.  This limit is specified with the Postfix <a href="postconf.5.html#max_use">max_use</a>
configuration parameter.

<li> Upon the onset of another delivery request, the LMTP server
associated with the current session does not respond to the RSET
command.

</ul>

<p>
Most of these limitations will be removed after Postfix implements
a connection cache that is shared among multiple LMTP client
programs.
</p>


</DD>

<DT><b><a name="lmtp_cname_overrides_servername">lmtp_cname_overrides_servername</a>
(default: yes)</b></DT><DD>

<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_cname_overrides_servername">smtp_cname_overrides_servername</a>
configuration parameter.  See there for details. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="lmtp_connect_timeout">lmtp_connect_timeout</a>
(default: 0s)</b></DT><DD>

<p> The LMTP client time limit for completing a TCP connection, or
zero (use the operating system built-in time limit).  When no
connection can be made within the deadline, the LMTP client tries
the next address on the mail exchanger list.  </p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>

<p>
Example:
</p>

<pre>
<a href="postconf.5.html#lmtp_connect_timeout">lmtp_connect_timeout</a> = 30s
</pre>


</DD>

<DT><b><a name="lmtp_connection_cache_destinations">lmtp_connection_cache_destinations</a>
(default: empty)</b></DT><DD>

<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_connection_cache_destinations">smtp_connection_cache_destinations</a>
configuration parameter.  See there for details. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="lmtp_connection_cache_on_demand">lmtp_connection_cache_on_demand</a>
(default: yes)</b></DT><DD>

<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_connection_cache_on_demand">smtp_connection_cache_on_demand</a>
configuration parameter.  See there for details. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="lmtp_connection_cache_time_limit">lmtp_connection_cache_time_limit</a>
(default: 2s)</b></DT><DD>

<p> The LMTP-specific version of the
<a href="postconf.5.html#smtp_connection_cache_time_limit">smtp_connection_cache_time_limit</a> configuration parameter.
See there for details. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="lmtp_connection_reuse_time_limit">lmtp_connection_reuse_time_limit</a>
(default: 300s)</b></DT><DD>

<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_connection_reuse_time_limit">smtp_connection_reuse_time_limit</a>
configuration parameter.  See there for details. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="lmtp_data_done_timeout">lmtp_data_done_timeout</a>
(default: 600s)</b></DT><DD>

<p> The LMTP client time limit for sending the LMTP ".", and for
receiving the server response.  When no response is received within
the deadline, a warning is logged that the mail may be delivered
multiple times.  </p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>


</DD>

<DT><b><a name="lmtp_data_init_timeout">lmtp_data_init_timeout</a>
(default: 120s)</b></DT><DD>

<p>
The LMTP client time limit for sending the LMTP DATA command, and
for receiving the server response.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>


</DD>

<DT><b><a name="lmtp_data_xfer_timeout">lmtp_data_xfer_timeout</a>
(default: 180s)</b></DT><DD>

<p>
The LMTP client time limit for sending the LMTP message content.
When the connection stalls for more than $<a href="postconf.5.html#lmtp_data_xfer_timeout">lmtp_data_xfer_timeout</a>
the LMTP client terminates the transfer.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>


</DD>

<DT><b><a name="lmtp_defer_if_no_mx_address_found">lmtp_defer_if_no_mx_address_found</a>
(default: no)</b></DT><DD>

<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_defer_if_no_mx_address_found">smtp_defer_if_no_mx_address_found</a>
configuration parameter.  See there for details. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="lmtp_destination_concurrency_limit">lmtp_destination_concurrency_limit</a>
(default: $<a href="postconf.5.html#default_destination_concurrency_limit">default_destination_concurrency_limit</a>)</b></DT><DD>

<p> The maximal number of parallel deliveries to the same destination
via the lmtp message delivery transport. This limit is enforced by
the queue manager. The message delivery transport name is the first
field in the entry in the <a href="master.5.html">master.cf</a> file.  </p>


</DD>

<DT><b><a name="lmtp_destination_recipient_limit">lmtp_destination_recipient_limit</a>
(default: $<a href="postconf.5.html#default_destination_recipient_limit">default_destination_recipient_limit</a>)</b></DT><DD>

<p> The maximal number of recipients per delivery via the lmtp
message delivery transport. This limit is enforced by the queue
manager. The message delivery transport name is the first field in
the entry in the <a href="master.5.html">master.cf</a> file.  </p>

<p> Setting this parameter to a value of 1 changes the meaning of
<a href="postconf.5.html#lmtp_destination_concurrency_limit">lmtp_destination_concurrency_limit</a> from concurrency per domain into
concurrency per recipient.  </p>


</DD>

<DT><b><a name="lmtp_discard_lhlo_keyword_address_maps">lmtp_discard_lhlo_keyword_address_maps</a>
(default: empty)</b></DT><DD>

<p> Lookup tables, indexed by the remote LMTP server address, with
case insensitive lists of LHLO keywords (pipelining, starttls,
auth, etc.) that the LMTP client will ignore in the LHLO response
from a remote LMTP server. See <a href="postconf.5.html#lmtp_discard_lhlo_keywords">lmtp_discard_lhlo_keywords</a> for
details. The table is not indexed by hostname for consistency with
<a href="postconf.5.html#smtpd_discard_ehlo_keyword_address_maps">smtpd_discard_ehlo_keyword_address_maps</a>. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="lmtp_discard_lhlo_keywords">lmtp_discard_lhlo_keywords</a>
(default: empty)</b></DT><DD>

<p> A case insensitive list of LHLO keywords (pipelining, starttls,
auth, etc.) that the LMTP client will ignore in the LHLO response
from a remote LMTP server. </p>

<p> This feature is available in Postfix 2.3 and later. </p>

<p> Notes: </p>

<ul>

<li> <p> Specify the <b>silent-discard</b> pseudo keyword to prevent
this action from being logged. </p>

<li> <p> Use the <a href="postconf.5.html#lmtp_discard_lhlo_keyword_address_maps">lmtp_discard_lhlo_keyword_address_maps</a> feature to
discard LHLO keywords selectively. </p>

</ul>


</DD>

<DT><b><a name="lmtp_enforce_tls">lmtp_enforce_tls</a>
(default: no)</b></DT><DD>

<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_enforce_tls">smtp_enforce_tls</a> configuration
parameter.  See there for details. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="lmtp_generic_maps">lmtp_generic_maps</a>
(default: empty)</b></DT><DD>

<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_generic_maps">smtp_generic_maps</a> configuration
parameter.  See there for details. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="lmtp_host_lookup">lmtp_host_lookup</a>
(default: dns)</b></DT><DD>

<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_host_lookup">smtp_host_lookup</a> configuration
parameter.  See there for details. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="lmtp_lhlo_name">lmtp_lhlo_name</a>
(default: $<a href="postconf.5.html#myhostname">myhostname</a>)</b></DT><DD>

<p>
The hostname to send in the LMTP LHLO command.
</p>

<p>
The default value is the machine hostname.  Specify a hostname or
[ip.add.re.ss].
</p>

<p>
This information can be specified in the <a href="postconf.5.html">main.cf</a> file for all LMTP
clients, or it can be specified in the <a href="master.5.html">master.cf</a> file for a specific
client, for example:
</p>

<blockquote>
<pre>
/etc/postfix/<a href="master.5.html">master.cf</a>:
    mylmtp ... lmtp -o <a href="postconf.5.html#lmtp_lhloname">lmtp_lhlo_name</a>=foo.bar.com
</pre>
</blockquote>

<p>
This feature is available in Postfix 2.3 and later.
</p>


</DD>

<DT><b><a name="lmtp_lhlo_timeout">lmtp_lhlo_timeout</a>
(default: 300s)</b></DT><DD>

<p> The LMTP client time limit for sending the LHLO command, and
for receiving the initial server response. </p>

<p> Time units: s (seconds), m (minutes), h (hours), d (days), w
(weeks).  The default time unit is s (seconds).  </p>


</DD>

<DT><b><a name="lmtp_line_length_limit">lmtp_line_length_limit</a>
(default: 990)</b></DT><DD>

<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_line_length_limit">smtp_line_length_limit</a>
configuration parameter.  See there for details. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="lmtp_mail_timeout">lmtp_mail_timeout</a>
(default: 300s)</b></DT><DD>

<p>
The LMTP client time limit for sending the MAIL FROM command, and
for receiving the server response.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>


</DD>

<DT><b><a name="lmtp_mx_address_limit">lmtp_mx_address_limit</a>
(default: 5)</b></DT><DD>

<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_mx_address_limit">smtp_mx_address_limit</a> configuration
parameter.  See there for details. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="lmtp_mx_session_limit">lmtp_mx_session_limit</a>
(default: 2)</b></DT><DD>

<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_mx_session_limit">smtp_mx_session_limit</a> configuration
parameter.  See there for details. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="lmtp_pix_workaround_delay_time">lmtp_pix_workaround_delay_time</a>
(default: 10s)</b></DT><DD>

<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_pix_workaround_delay_time">smtp_pix_workaround_delay_time</a>
configuration parameter.  See there for details. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="lmtp_pix_workaround_maps">lmtp_pix_workaround_maps</a>
(default: empty)</b></DT><DD>

<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_pix_workaround_maps">smtp_pix_workaround_maps</a>
configuration parameter.  See there for details. </p>

<p> This feature is available in Postfix 2.4 and later. </p>


</DD>

<DT><b><a name="lmtp_pix_workaround_threshold_time">lmtp_pix_workaround_threshold_time</a>
(default: 500s)</b></DT><DD>

<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_pix_workaround_threshold_time">smtp_pix_workaround_threshold_time</a>
configuration parameter.  See there for details. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="lmtp_pix_workarounds">lmtp_pix_workarounds</a>
(default: empty)</b></DT><DD>

<p> The LMTP-specific version of the smtp_pix_workaround
configuration parameter.  See there for details. </p>

<p> This feature is available in Postfix 2.4 and later. </p>


</DD>

<DT><b><a name="lmtp_quit_timeout">lmtp_quit_timeout</a>
(default: 300s)</b></DT><DD>

<p>
The LMTP client time limit for sending the QUIT command, and for
receiving the server response.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>


</DD>

<DT><b><a name="lmtp_quote_rfc821_envelope">lmtp_quote_rfc821_envelope</a>
(default: yes)</b></DT><DD>

<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_quote_rfc821_envelope">smtp_quote_rfc821_envelope</a>
configuration parameter.  See there for details. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="lmtp_randomize_addresses">lmtp_randomize_addresses</a>
(default: yes)</b></DT><DD>

<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_randomize_addresses">smtp_randomize_addresses</a>
configuration parameter.  See there for details. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="lmtp_rcpt_timeout">lmtp_rcpt_timeout</a>
(default: 300s)</b></DT><DD>

<p>
The LMTP client time limit for sending the RCPT TO command, and
for receiving the server response.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>


</DD>

<DT><b><a name="lmtp_rset_timeout">lmtp_rset_timeout</a>
(default: 20s)</b></DT><DD>

<p> The LMTP client time limit for sending the RSET command, and
for receiving the server response. The LMTP client sends RSET in
order to finish a recipient address probe, or to verify that a
cached connection is still alive.  </p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>


</DD>

<DT><b><a name="lmtp_sasl_auth_cache_name">lmtp_sasl_auth_cache_name</a>
(default: empty)</b></DT><DD>

<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_sasl_auth_cache_name">smtp_sasl_auth_cache_name</a>
configuration parameter.  See there for details. </p>

<p> This feature is available in Postfix 2.5 and later. </p>


</DD>

<DT><b><a name="lmtp_sasl_auth_cache_time">lmtp_sasl_auth_cache_time</a>
(default: 90d)</b></DT><DD>

<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_sasl_auth_cache_time">smtp_sasl_auth_cache_time</a>
configuration parameter.  See there for details. </p>

<p> This feature is available in Postfix 2.5 and later. </p>


</DD>

<DT><b><a name="lmtp_sasl_auth_enable">lmtp_sasl_auth_enable</a>
(default: no)</b></DT><DD>

<p>
Enable SASL authentication in the Postfix LMTP client.
</p>


</DD>

<DT><b><a name="lmtp_sasl_auth_soft_bounce">lmtp_sasl_auth_soft_bounce</a>
(default: yes)</b></DT><DD>

<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_sasl_auth_soft_bounce">smtp_sasl_auth_soft_bounce</a>
configuration parameter.  See there for details. </p>

<p> This feature is available in Postfix 2.5 and later. </p>


</DD>

<DT><b><a name="lmtp_sasl_mechanism_filter">lmtp_sasl_mechanism_filter</a>
(default: empty)</b></DT><DD>

<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_sasl_mechanism_filter">smtp_sasl_mechanism_filter</a>
configuration parameter.  See there for details. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="lmtp_sasl_password_maps">lmtp_sasl_password_maps</a>
(default: empty)</b></DT><DD>

<p>
Optional LMTP client lookup tables with one username:password entry
per host or domain.  If a remote host or domain has no username:password
entry, then the Postfix LMTP client will not attempt to authenticate
to the remote host.
</p>


</DD>

<DT><b><a name="lmtp_sasl_path">lmtp_sasl_path</a>
(default: empty)</b></DT><DD>

<p> Implementation-specific information that is passed through to
the SASL plug-in implementation that is selected with
<b><a href="postconf.5.html#lmtp_sasl_type">lmtp_sasl_type</a></b>.  Typically this specifies the name of a
configuration file or rendezvous point. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="lmtp_sasl_security_options">lmtp_sasl_security_options</a>
(default: noplaintext, noanonymous)</b></DT><DD>

<p> SASL security options; as of Postfix 2.3 the list of available
features depends on the SASL client implementation that is selected
with <b><a href="postconf.5.html#lmtp_sasl_type">lmtp_sasl_type</a></b>.  </p>

<p> The following security features are defined for the <b>cyrus</b>
client SASL implementation: </p>

<dl>

<dt><b>noplaintext</b></dt>

<dd>Disallow authentication methods that use plaintext passwords. </dd>

<dt><b>noactive</b></dt>

<dd>Disallow authentication methods that are vulnerable to non-dictionary
active attacks. </dd>

<dt><b>nodictionary</b></dt>

<dd>Disallow authentication methods that are vulnerable to passive
dictionary attack. </dd>

<dt><b>noanonymous</b></dt>

<dd>Disallow anonymous logins. </dd>

</dl>

<p>
Example:
</p>

<pre>
<a href="postconf.5.html#lmtp_sasl_security_options">lmtp_sasl_security_options</a> = noplaintext
</pre>


</DD>

<DT><b><a name="lmtp_sasl_tls_security_options">lmtp_sasl_tls_security_options</a>
(default: $<a href="postconf.5.html#lmtp_sasl_security_options">lmtp_sasl_security_options</a>)</b></DT><DD>

<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_sasl_tls_security_options">smtp_sasl_tls_security_options</a>
configuration parameter.  See there for details. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="lmtp_sasl_tls_verified_security_options">lmtp_sasl_tls_verified_security_options</a>
(default: $<a href="postconf.5.html#lmtp_sasl_tls_security_options">lmtp_sasl_tls_security_options</a>)</b></DT><DD>

<p> The LMTP-specific version of the
<a href="postconf.5.html#smtp_sasl_tls_verified_security_options">smtp_sasl_tls_verified_security_options</a> configuration parameter.
See there for details. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="lmtp_sasl_type">lmtp_sasl_type</a>
(default: cyrus)</b></DT><DD>

<p> The SASL plug-in type that the Postfix LMTP client should use
for authentication.  The available types are listed with the
"<b>postconf -A</b>" command. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="lmtp_send_xforward_command">lmtp_send_xforward_command</a>
(default: no)</b></DT><DD>

<p>
Send an XFORWARD command to the LMTP server when the LMTP LHLO
server response announces XFORWARD support.  This allows an <a href="lmtp.8.html">lmtp(8)</a>
delivery agent, used for content filter message injection, to
forward the name, address, protocol and HELO name of the original
client to the content filter and downstream queuing LMTP server.
Before you change the value to yes, it is best to make sure that
your content filter supports this command.
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>


</DD>

<DT><b><a name="lmtp_sender_dependent_authentication">lmtp_sender_dependent_authentication</a>
(default: no)</b></DT><DD>

<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_sender_dependent_authentication">smtp_sender_dependent_authentication</a>
configuration parameter.  See there for details. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="lmtp_skip_5xx_greeting">lmtp_skip_5xx_greeting</a>
(default: yes)</b></DT><DD>

<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_skip_5xx_greeting">smtp_skip_5xx_greeting</a>
configuration parameter.  See there for details. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="lmtp_skip_quit_response">lmtp_skip_quit_response</a>
(default: no)</b></DT><DD>

<p>
Wait for the response to the LMTP QUIT command.
</p>


</DD>

<DT><b><a name="lmtp_starttls_timeout">lmtp_starttls_timeout</a>
(default: 300s)</b></DT><DD>

<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_starttls_timeout">smtp_starttls_timeout</a> configuration
parameter.  See there for details. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="lmtp_tcp_port">lmtp_tcp_port</a>
(default: 24)</b></DT><DD>

<p>
The default TCP port that the Postfix LMTP client connects to.
</p>


</DD>

<DT><b><a name="lmtp_tls_CAfile">lmtp_tls_CAfile</a>
(default: empty)</b></DT><DD>

<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_CAfile">smtp_tls_CAfile</a>
configuration parameter.  See there for details. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="lmtp_tls_CApath">lmtp_tls_CApath</a>
(default: empty)</b></DT><DD>

<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_CApath">smtp_tls_CApath</a>
configuration parameter.  See there for details. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="lmtp_tls_cert_file">lmtp_tls_cert_file</a>
(default: empty)</b></DT><DD>

<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_cert_file">smtp_tls_cert_file</a>
configuration parameter.  See there for details. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="lmtp_tls_dcert_file">lmtp_tls_dcert_file</a>
(default: empty)</b></DT><DD>

<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_dcert_file">smtp_tls_dcert_file</a>
configuration parameter.  See there for details. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="lmtp_tls_dkey_file">lmtp_tls_dkey_file</a>
(default: $<a href="postconf.5.html#lmtp_tls_dcert_file">lmtp_tls_dcert_file</a>)</b></DT><DD>

<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_dkey_file">smtp_tls_dkey_file</a>
configuration parameter.  See there for details. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="lmtp_tls_enforce_peername">lmtp_tls_enforce_peername</a>
(default: yes)</b></DT><DD>

<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_enforce_peername">smtp_tls_enforce_peername</a>
configuration parameter.  See there for details. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="lmtp_tls_exclude_ciphers">lmtp_tls_exclude_ciphers</a>
(default: empty)</b></DT><DD>

<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_exclude_ciphers">smtp_tls_exclude_ciphers</a>
configuration parameter.  See there for details. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="lmtp_tls_fingerprint_cert_match">lmtp_tls_fingerprint_cert_match</a>
(default: empty)</b></DT><DD>

<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_fingerprint_cert_match">smtp_tls_fingerprint_cert_match</a>
configuration parameter.  See there for details. </p>

<p> This feature is available in Postfix 2.5 and later. </p>


</DD>

<DT><b><a name="lmtp_tls_fingerprint_digest">lmtp_tls_fingerprint_digest</a>
(default: md5)</b></DT><DD>

<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_fingerprint_digest">smtp_tls_fingerprint_digest</a>
configuration parameter.  See there for details. </p>

<p> This feature is available in Postfix 2.5 and later. </p>


</DD>

<DT><b><a name="lmtp_tls_key_file">lmtp_tls_key_file</a>
(default: $<a href="postconf.5.html#lmtp_tls_cert_file">lmtp_tls_cert_file</a>)</b></DT><DD>

<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_key_file">smtp_tls_key_file</a>
configuration parameter.  See there for details. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="lmtp_tls_loglevel">lmtp_tls_loglevel</a>
(default: 0)</b></DT><DD>

<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_loglevel">smtp_tls_loglevel</a>
configuration parameter.  See there for details. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="lmtp_tls_mandatory_ciphers">lmtp_tls_mandatory_ciphers</a>
(default: empty)</b></DT><DD>

<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_mandatory_ciphers">smtp_tls_mandatory_ciphers</a>
configuration parameter.  See there for details. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="lmtp_tls_mandatory_exclude_ciphers">lmtp_tls_mandatory_exclude_ciphers</a>
(default: empty)</b></DT><DD>

<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_mandatory_exclude_ciphers">smtp_tls_mandatory_exclude_ciphers</a>
configuration parameter.  See there for details. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="lmtp_tls_mandatory_protocols">lmtp_tls_mandatory_protocols</a>
(default: SSLv3, TLSv1)</b></DT><DD>

<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_mandatory_protocols">smtp_tls_mandatory_protocols</a>
configuration parameter. See there for details. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="lmtp_tls_note_starttls_offer">lmtp_tls_note_starttls_offer</a>
(default: no)</b></DT><DD>

<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_note_starttls_offer">smtp_tls_note_starttls_offer</a>
configuration parameter.  See there for details. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="lmtp_tls_per_site">lmtp_tls_per_site</a>
(default: empty)</b></DT><DD>

<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_per_site">smtp_tls_per_site</a> configuration
parameter.  See there for details. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="lmtp_tls_policy_maps">lmtp_tls_policy_maps</a>
(default: empty)</b></DT><DD>

<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_policy_maps">smtp_tls_policy_maps</a>
configuration parameter. See there for details. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="lmtp_tls_scert_verifydepth">lmtp_tls_scert_verifydepth</a>
(default: 9)</b></DT><DD>

<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_scert_verifydepth">smtp_tls_scert_verifydepth</a>
configuration parameter.  See there for details. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="lmtp_tls_secure_cert_match">lmtp_tls_secure_cert_match</a>
(default: nexthop)</b></DT><DD>

<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_secure_cert_match">smtp_tls_secure_cert_match</a>
configuration parameter. See there for details. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="lmtp_tls_security_level">lmtp_tls_security_level</a>
(default: empty)</b></DT><DD>

<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_security_level">smtp_tls_security_level</a> configuration
parameter.  See there for details. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="lmtp_tls_session_cache_database">lmtp_tls_session_cache_database</a>
(default: empty)</b></DT><DD>

<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_session_cache_database">smtp_tls_session_cache_database</a>
configuration parameter. See there for details. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="lmtp_tls_session_cache_timeout">lmtp_tls_session_cache_timeout</a>
(default: 3600s)</b></DT><DD>

<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_session_cache_timeout">smtp_tls_session_cache_timeout</a>
configuration parameter.  See there for details. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="lmtp_tls_verify_cert_match">lmtp_tls_verify_cert_match</a>
(default: hostname)</b></DT><DD>

<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_verify_cert_match">smtp_tls_verify_cert_match</a>
configuration parameter. See there for details. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="lmtp_use_tls">lmtp_use_tls</a>
(default: no)</b></DT><DD>

<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_use_tls">smtp_use_tls</a> configuration
parameter.  See there for details. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="lmtp_xforward_timeout">lmtp_xforward_timeout</a>
(default: 300s)</b></DT><DD>

<p>
The LMTP client time limit for sending the XFORWARD command, and
for receiving the server response.
</p>

<p>
In case of problems the client does NOT try the next address on
the mail exchanger list.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>


</DD>

<DT><b><a name="local_command_shell">local_command_shell</a>
(default: empty)</b></DT><DD>

<p>
Optional shell program for <a href="local.8.html">local(8)</a> delivery to non-Postfix command.
By default, non-Postfix commands are executed directly; commands
are given to given to /bin/sh only when they contain shell meta
characters or shell built-in commands.  </p>

<p> "sendmail's restricted shell" (smrsh) is what most people will
use in order to restrict what programs can be run from e.g. .forward
files (smrsh is part of the Sendmail distribution).  </p>

<p> Note: when a shell program is specified, it is invoked even
when the command contains no shell built-in commands or meta
characters.  </p>

<p>
Example:
</p>

<pre>
<a href="postconf.5.html#local_command_shell">local_command_shell</a> = /some/where/smrsh -c
</pre>


</DD>

<DT><b><a name="local_destination_concurrency_limit">local_destination_concurrency_limit</a>
(default: 2)</b></DT><DD>

<p> The maximal number of parallel deliveries via the local mail
delivery transport to the same recipient (when
"<a href="postconf.5.html#local_destination_recipient_limit">local_destination_recipient_limit</a> = 1") or the maximal number of
parallel deliveries to the same <a href="ADDRESS_CLASS_README.html#local_domain_class">local domain</a> (when
"<a href="postconf.5.html#local_destination_recipient_limit">local_destination_recipient_limit</a> &gt; 1"). This limit is enforced by
the queue manager. The message delivery transport name is the first
field in the entry in the <a href="master.5.html">master.cf</a> file. </p>

<p> A low limit of 2 is recommended, just in case someone has an
expensive shell command in a .forward file or in an alias (e.g.,
a mailing list manager).  You don't want to run lots of those at
the same time.  </p>


</DD>

<DT><b><a name="local_destination_recipient_limit">local_destination_recipient_limit</a>
(default: 1)</b></DT><DD>

<p> The maximal number of recipients per message delivery via the
local mail delivery transport. This limit is enforced by the queue
manager. The message delivery transport name is the first field in
the entry in the <a href="master.5.html">master.cf</a> file. </p>

<p> Setting this parameter to a value &gt; 1 changes the meaning of
<a href="postconf.5.html#local_destination_concurrency_limit">local_destination_concurrency_limit</a> from concurrency per recipient
into concurrency per domain.  </p>


</DD>

<DT><b><a name="local_header_rewrite_clients">local_header_rewrite_clients</a>
(default: <a href="postconf.5.html#permit_inet_interfaces">permit_inet_interfaces</a>)</b></DT><DD>

<p> Rewrite message header addresses in mail from these clients and
update incomplete addresses with the domain name in $<a href="postconf.5.html#myorigin">myorigin</a> or
$<a href="postconf.5.html#mydomain">mydomain</a>; either don't rewrite message headers from other clients
at all, or rewrite message headers and update incomplete addresses
with the domain specified in the <a href="postconf.5.html#remote_header_rewrite_domain">remote_header_rewrite_domain</a>
parameter.  </p>

<p> See the <a href="postconf.5.html#append_at_myorigin">append_at_myorigin</a> and <a href="postconf.5.html#append_dot_mydomain">append_dot_mydomain</a> parameters
for details of how domain names are appended to incomplete addresses.
</p>

<p> Specify a list of zero or more of the following:  </p>

<dl>

<dt><b><a href="postconf.5.html#permit_inet_interfaces">permit_inet_interfaces</a></b></dt>

<dd> Append the domain name in $<a href="postconf.5.html#myorigin">myorigin</a> or $<a href="postconf.5.html#mydomain">mydomain</a> when the
client IP address matches $<a href="postconf.5.html#inet_interfaces">inet_interfaces</a>. This is enabled by
default. </dd>

<dt><b><a href="postconf.5.html#permit_mynetworks">permit_mynetworks</a></b></dt>

<dd> Append the domain name in $<a href="postconf.5.html#myorigin">myorigin</a> or $<a href="postconf.5.html#mydomain">mydomain</a> when the
client IP address matches any network or network address listed in
$<a href="postconf.5.html#mynetworks">mynetworks</a>. This setting will not prevent remote mail header
address rewriting when mail from a remote client is forwarded by
a neighboring system.  </dd>

<dt><b><a href="postconf.5.html#permit_sasl_authenticated">permit_sasl_authenticated</a> </b></dt>

<dd> Append the domain name in $<a href="postconf.5.html#myorigin">myorigin</a> or $<a href="postconf.5.html#mydomain">mydomain</a> when the
client is successfully authenticated via the <a href="http://tools.ietf.org/html/rfc4954">RFC 4954</a> (AUTH)
protocol. </dd>

<dt><b><a href="postconf.5.html#permit_tls_clientcerts">permit_tls_clientcerts</a> </b></dt>

<dd> Append the domain name in $<a href="postconf.5.html#myorigin">myorigin</a> or $<a href="postconf.5.html#mydomain">mydomain</a> when the
client TLS certificate fingerprint is listed in $<a href="postconf.5.html#relay_clientcerts">relay_clientcerts</a>.
The fingerprint digest algorithm is configurable via the
<a href="postconf.5.html#smtpd_tls_fingerprint_digest">smtpd_tls_fingerprint_digest</a> parameter (hard-coded as md5 prior to
Postfix version 2.5).  </dd>

<dt><b><a href="postconf.5.html#permit_tls_all_clientcerts">permit_tls_all_clientcerts</a> </b></dt>

<dd> Append the domain name in $<a href="postconf.5.html#myorigin">myorigin</a> or $<a href="postconf.5.html#mydomain">mydomain</a> when the
client TLS certificate is successfully verified, regardless of
whether it is listed on the server, and regardless of the certifying
authority. </dd>

<dt><b><a name="check_address_map">check_address_map</a> <i><a href="DATABASE_README.html">type:table</a></i> </b></dt>

<dt><b><i><a href="DATABASE_README.html">type:table</a></i> </b></dt>

<dd> Append the domain name in $<a href="postconf.5.html#myorigin">myorigin</a> or $<a href="postconf.5.html#mydomain">mydomain</a> when the
client IP address matches the specified lookup table.
The lookup result is ignored, and no subnet lookup is done. This
is suitable for, e.g., pop-before-smtp lookup tables. </dd>

</dl>

<p> Examples:  </p>

<p> The Postfix &lt; 2.2 backwards compatible setting: always rewrite
message headers, and always append my own domain to incomplete
header addresses.  </p>

<blockquote>
<pre>
<a href="postconf.5.html#local_header_rewrite_clients">local_header_rewrite_clients</a> = static:all
</pre>
</blockquote>

<p> The purist (and default) setting: rewrite headers only in mail
from Postfix sendmail and in SMTP mail from this machine. </p>

<blockquote>
<pre>
<a href="postconf.5.html#local_header_rewrite_clients">local_header_rewrite_clients</a> = <a href="postconf.5.html#permit_inet_interfaces">permit_inet_interfaces</a>
</pre>
</blockquote>

<p> The intermediate setting: rewrite header addresses and append
$<a href="postconf.5.html#myorigin">myorigin</a> or $<a href="postconf.5.html#mydomain">mydomain</a> information only with mail from Postfix
sendmail, from local clients, or from authorized SMTP clients. </p>

<p> Note: this setting will not prevent remote mail header address
rewriting when mail from a remote client is forwarded by a neighboring
system.  </p>

<blockquote>
<pre>
<a href="postconf.5.html#local_header_rewrite_clients">local_header_rewrite_clients</a> = <a href="postconf.5.html#permit_mynetworks">permit_mynetworks</a>,
    <a href="postconf.5.html#permit_sasl_authenticated">permit_sasl_authenticated</a> <a href="postconf.5.html#permit_tls_clientcerts">permit_tls_clientcerts</a>
    <a href="postconf.5.html#check_address_map">check_address_map</a> hash:/etc/postfix/pop-before-smtp
</pre>
</blockquote>


</DD>

<DT><b><a name="local_recipient_maps">local_recipient_maps</a>
(default: <a href="proxymap.8.html">proxy</a>:unix:passwd.byname $<a href="postconf.5.html#alias_maps">alias_maps</a>)</b></DT><DD>

<p> Lookup tables with all names or addresses of local recipients:
a recipient address is local when its domain matches $<a href="postconf.5.html#mydestination">mydestination</a>,
$<a href="postconf.5.html#inet_interfaces">inet_interfaces</a> or $<a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a>.  Specify @domain as a
wild-card for domains that do not have a valid recipient list.
Technically, tables listed with $<a href="postconf.5.html#local_recipient_maps">local_recipient_maps</a> are used as
lists: Postfix needs to know only if a lookup string is found or
not, but it does not use the result from table lookup.  </p>

<p>
If this parameter is non-empty (the default), then the Postfix SMTP
server will reject mail for unknown local users.
</p>

<p>
To turn off local recipient checking in the Postfix SMTP server,
specify "<a href="postconf.5.html#local_recipient_maps">local_recipient_maps</a> =" (i.e. empty).
</p>

<p>
The default setting assumes that you use the default Postfix local
delivery agent for local delivery. You need to update the
<a href="postconf.5.html#local_recipient_maps">local_recipient_maps</a> setting if:
</p>

<ul>

<li>You redefine the local delivery agent in <a href="master.5.html">master.cf</a>.

<li>You redefine the "<a href="postconf.5.html#local_transport">local_transport</a>" setting in <a href="postconf.5.html">main.cf</a>.

<li>You use the "<a href="postconf.5.html#luser_relay">luser_relay</a>", "<a href="postconf.5.html#mailbox_transport">mailbox_transport</a>", or "<a href="postconf.5.html#fallback_transport">fallback_transport</a>"
feature of the Postfix <a href="local.8.html">local(8)</a> delivery agent.

</ul>

<p>
Details are described in the <a href="LOCAL_RECIPIENT_README.html">LOCAL_RECIPIENT_README</a> file.
</p>

<p>
Beware: if the Postfix SMTP server runs chrooted, you need to access
the passwd file via the <a href="proxymap.8.html">proxymap(8)</a> service, in order to overcome
chroot access restrictions. The alternative, maintaining a copy of
the system password file in the chroot jail is not practical.
</p>

<p>
Examples:
</p>

<pre>
<a href="postconf.5.html#local_recipient_maps">local_recipient_maps</a> =
</pre>


</DD>

<DT><b><a name="local_transport">local_transport</a>
(default: <a href="local.8.html">local</a>:$<a href="postconf.5.html#myhostname">myhostname</a>)</b></DT><DD>

<p> The default mail delivery transport and next-hop destination
for final delivery to domains listed with <a href="postconf.5.html#mydestination">mydestination</a>, and for
[ipaddress] destinations that match $<a href="postconf.5.html#inet_interfaces">inet_interfaces</a> or $<a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a>.
This information can be overruled with the <a href="transport.5.html">transport(5)</a> table. </p>

<p>
By default, local mail is delivered to the transport called "local",
which is just the name of a service that is defined the <a href="master.5.html">master.cf</a> file.
</p>

<p>
Specify a string of the form <i>transport:nexthop</i>, where <i>transport</i>
is the name of a mail delivery transport defined in <a href="master.5.html">master.cf</a>.
The <i>:nexthop</i> part is optional.  For more details see the
<a href="transport.5.html">transport(5)</a> manual page.
</p>

<p>
Beware: if you override the default local delivery agent then you
need to review the <a href="LOCAL_RECIPIENT_README.html">LOCAL_RECIPIENT_README</a> document, otherwise the
SMTP server may reject mail for local recipients.
</p>


</DD>

<DT><b><a name="luser_relay">luser_relay</a>
(default: empty)</b></DT><DD>

<p>
Optional catch-all destination for unknown <a href="local.8.html">local(8)</a> recipients.
By default, mail for unknown recipients in domains that match
$<a href="postconf.5.html#mydestination">mydestination</a>, $<a href="postconf.5.html#inet_interfaces">inet_interfaces</a> or $<a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a> is returned
as undeliverable.
</p>

<p>
The following $name expansions are done on <a href="postconf.5.html#luser_relay">luser_relay</a>:
</p>

<dl>

<dt><b>$domain</b></dt>

<dd>The recipient domain. </dd>

<dt><b>$extension</b></dt>

<dd>The recipient address extension. </dd>

<dt><b>$home</b></dt>

<dd>The recipient's home directory. </dd>

<dt><b>$local</b></dt>

<dd>The entire recipient address localpart. </dd>

<dt><b>$recipient</b></dt>

<dd>The full recipient address. </dd>

<dt><b>$<a href="postconf.5.html#recipient_delimiter">recipient_delimiter</a></b></dt>

<dd>The system-wide recipient address extension delimiter. </dd>

<dt><b>$shell</b></dt>

<dd>The recipient's login shell. </dd>

<dt><b>$user</b></dt>

<dd>The recipient username. </dd>

<dt><b>${name?value}</b></dt>

<dd>Expands to <i>value</i> when <i>$name</i> has a non-empty value. </dd>

<dt><b>${name:value}</b></dt>

<dd>Expands to <i>value</i> when <i>$name</i> has an empty value. </dd>

</dl>

<p>
Instead of $name you can also specify ${name} or $(name).
</p>

<p>
Note: <a href="postconf.5.html#luser_relay">luser_relay</a> works only for the Postfix <a href="local.8.html">local(8)</a> delivery agent.
</p>

<p>
Note: if you use this feature for accounts not in the UNIX password
file, then you must specify "<a href="postconf.5.html#local_recipient_maps">local_recipient_maps</a> =" (i.e. empty)
in the <a href="postconf.5.html">main.cf</a> file, otherwise the Postfix SMTP server will reject mail
for non-UNIX accounts with "User unknown in local recipient table".
</p>

<p>
Examples:
</p>

<pre>
<a href="postconf.5.html#luser_relay">luser_relay</a> = $user@other.host
<a href="postconf.5.html#luser_relay">luser_relay</a> = $local@other.host
<a href="postconf.5.html#luser_relay">luser_relay</a> = admin+$local
</pre>


</DD>

<DT><b><a name="mail_name">mail_name</a>
(default: Postfix)</b></DT><DD>

<p>
The mail system name that is displayed in Received: headers, in
the SMTP greeting banner, and in bounced mail.
</p>


</DD>

<DT><b><a name="mail_owner">mail_owner</a>
(default: postfix)</b></DT><DD>

<p>
The UNIX system account that owns the Postfix queue and most Postfix
daemon processes.  Specify the name of a user account that does
not share a group with other accounts and that owns no other files
or processes on the system.  In particular, don't specify nobody
or daemon.  PLEASE USE A DEDICATED USER ID AND GROUP ID.
</p>

<p>
When this parameter value is changed you need to re-run "<b>postfix
set-permissions</b>" (with Postfix version 2.0 and earlier:
"<b>/etc/postfix/post-install set-permissions</b>".
</p>


</DD>

<DT><b><a name="mail_release_date">mail_release_date</a>
(default: see "postconf -d" output)</b></DT><DD>

<p>
The Postfix release date, in "YYYYMMDD" format.
</p>


</DD>

<DT><b><a name="mail_spool_directory">mail_spool_directory</a>
(default: see "postconf -d" output)</b></DT><DD>

<p>
The directory where <a href="local.8.html">local(8)</a> UNIX-style mailboxes are kept. The
default setting depends on the system type. Specify a name ending
in / for maildir-style delivery.
</p>

<p>
Note: maildir delivery is done with the privileges of the recipient.
If you use the <a href="postconf.5.html#mail_spool_directory">mail_spool_directory</a> setting for maildir style
delivery, then you must create the top-level maildir directory in
advance. Postfix will not create it.
</p>

<p>
Examples:
</p>

<pre>
<a href="postconf.5.html#mail_spool_directory">mail_spool_directory</a> = /var/mail
<a href="postconf.5.html#mail_spool_directory">mail_spool_directory</a> = /var/spool/mail
</pre>


</DD>

<DT><b><a name="mail_version">mail_version</a>
(default: see "postconf -d" output)</b></DT><DD>

<p>
The version of the mail system. Stable releases are named
<i>major</i>.<i>minor</i>.<i>patchlevel</i>. Experimental releases
also include the release date. The version string can be used in,
for example, the SMTP greeting banner.
</p>


</DD>

<DT><b><a name="mailbox_command">mailbox_command</a>
(default: empty)</b></DT><DD>

<p>
Optional external command that the <a href="local.8.html">local(8)</a> delivery agent should
use for mailbox delivery.  The command is run with the user ID and
the primary group ID privileges of the recipient.  Exception:
command delivery for root executes with $<a href="postconf.5.html#default_privs">default_privs</a> privileges.
This is not a problem, because 1) mail for root should always be
aliased to a real user and 2) don't log in as root, use "su" instead.
</p>

<p>
The following environment variables are exported to the command:
</p>

<dl>

<dt><b>CLIENT_ADDRESS</b></dt>

<dd>Remote client network address. Available in Postfix version 2.2 and
later. </dd>

<dt><b>CLIENT_HELO</b></dt>

<dd>Remote client EHLO command parameter. Available in Postfix version 2.2
and later.</dd>

<dt><b>CLIENT_HOSTNAME</b></dt>

<dd>Remote client hostname. Available in Postfix version 2.2 and later.
</dd>

<dt><b>CLIENT_PROTOCOL</b></dt>

<dd>Remote client protocol. Available in Postfix version 2.2 and later.
</dd>

<dt><b>DOMAIN</b></dt>

<dd>The domain part of the recipient address. </dd>

<dt><b>EXTENSION</b></dt>

<dd>The optional address extension. </dd>

<dt><b>HOME</b></dt>

<dd>The recipient home directory. </dd>

<dt><b>LOCAL</b></dt>

<dd>The recipient address localpart. </dd>

<dt><b>LOGNAME</b></dt>

<dd>The recipient's username. </dd>

<dt><b>ORIGINAL_RECIPIENT</b></dt>

<dd>The entire recipient address, before any address rewriting or
aliasing.  </dd>

<dt><b>RECIPIENT</b></dt>

<dd>The full recipient address. </dd>

<dt><b>SASL_METHOD</b></dt>

<dd>SASL authentication method specified in the remote client AUTH
command. Available in Postfix version 2.2 and later. </dd>

<dt><b>SASL_SENDER</b></dt>

<dd>SASL sender address specified in the remote client MAIL FROM
command. Available in Postfix version 2.2 and later. </dd>

<dt><b>SASL_USER</b></dt>

<dd>SASL username specified in the remote client AUTH command.
Available in Postfix version 2.2 and later.  </dd>

<dt><b>SENDER</b></dt>

<dd>The full sender address. </dd>

<dt><b>SHELL</b></dt>

<dd>The recipient's login shell. </dd>

<dt><b>USER</b></dt>

<dd>The recipient username. </dd>

</dl>

<p>
Unlike other Postfix configuration parameters, the <a href="postconf.5.html#mailbox_command">mailbox_command</a>
parameter is not subjected to $name substitutions. This is to make
it easier to specify shell syntax (see example below).
</p>

<p>
If you can, avoid shell meta characters because they will force
Postfix to run an expensive shell process. If you're delivering
via Procmail then running a shell won't make a noticeable difference
in the total cost.
</p>

<p>
Note: if you use the <a href="postconf.5.html#mailbox_command">mailbox_command</a> feature to deliver mail
system-wide, you must set up an alias that forwards mail for root
to a real user.
</p>

<p> The precedence of <a href="local.8.html">local(8)</a> delivery features from high to low
is: aliases, .forward files, <a href="postconf.5.html#mailbox_transport_maps">mailbox_transport_maps</a>, <a href="postconf.5.html#mailbox_transport">mailbox_transport</a>,
<a href="postconf.5.html#mailbox_command_maps">mailbox_command_maps</a>, <a href="postconf.5.html#mailbox_command">mailbox_command</a>, <a href="postconf.5.html#home_mailbox">home_mailbox</a>, <a href="postconf.5.html#mail_spool_directory">mail_spool_directory</a>,
<a href="postconf.5.html#fallback_transport_maps">fallback_transport_maps</a>, <a href="postconf.5.html#fallback_transport">fallback_transport</a> and <a href="postconf.5.html#luser_relay">luser_relay</a>.  </p>

<p>
Examples:
</p>

<pre>
<a href="postconf.5.html#mailbox_command">mailbox_command</a> = /some/where/procmail
<a href="postconf.5.html#mailbox_command">mailbox_command</a> = /some/where/procmail -a "$EXTENSION"
<a href="postconf.5.html#mailbox_command">mailbox_command</a> = /some/where/maildrop -d "$USER"
        -f "$SENDER" "$EXTENSION"
</pre>


</DD>

<DT><b><a name="mailbox_command_maps">mailbox_command_maps</a>
(default: empty)</b></DT><DD>

<p>
Optional lookup tables with per-recipient external commands to use
for <a href="local.8.html">local(8)</a> mailbox delivery.  Behavior is as with <a href="postconf.5.html#mailbox_command">mailbox_command</a>.
</p>

<p> The precedence of <a href="local.8.html">local(8)</a> delivery features from high to low
is: aliases, .forward files, <a href="postconf.5.html#mailbox_transport_maps">mailbox_transport_maps</a>, <a href="postconf.5.html#mailbox_transport">mailbox_transport</a>,
<a href="postconf.5.html#mailbox_command_maps">mailbox_command_maps</a>, <a href="postconf.5.html#mailbox_command">mailbox_command</a>, <a href="postconf.5.html#home_mailbox">home_mailbox</a>, <a href="postconf.5.html#mail_spool_directory">mail_spool_directory</a>,
<a href="postconf.5.html#fallback_transport_maps">fallback_transport_maps</a>, <a href="postconf.5.html#fallback_transport">fallback_transport</a> and <a href="postconf.5.html#luser_relay">luser_relay</a>.  </p>


</DD>

<DT><b><a name="mailbox_delivery_lock">mailbox_delivery_lock</a>
(default: see "postconf -d" output)</b></DT><DD>

<p>
How to lock a UNIX-style <a href="local.8.html">local(8)</a> mailbox before attempting delivery.
For a list of available file locking methods, use the "<b>postconf
-l</b>" command.
</p>

<p>
This setting is ignored with <b>maildir</b> style delivery,
because such deliveries are safe without explicit locks.
</p>

<p>
Note: The <b>dotlock</b> method requires that the recipient UID or
GID has write access to the parent directory of the mailbox file.
</p>

<p>
Note: the default setting of this parameter is system dependent.
</p>


</DD>

<DT><b><a name="mailbox_size_limit">mailbox_size_limit</a>
(default: 51200000)</b></DT><DD>

<p> The maximal size of any <a href="local.8.html">local(8)</a> individual mailbox or maildir
file, or zero (no limit).  In fact, this limits the size of any
file that is written to upon local delivery, including files written
by external commands that are executed by the <a href="local.8.html">local(8)</a> delivery
agent.  </p>

<p>
This limit must not be smaller than the message size limit.
</p>


</DD>

<DT><b><a name="mailbox_transport">mailbox_transport</a>
(default: empty)</b></DT><DD>

<p>
Optional message delivery transport that the <a href="local.8.html">local(8)</a> delivery
agent should use for mailbox delivery to all local recipients,
whether or not they are found in the UNIX passwd database.
</p>

<p> The precedence of <a href="local.8.html">local(8)</a> delivery features from high to low
is: aliases, .forward files, <a href="postconf.5.html#mailbox_transport_maps">mailbox_transport_maps</a>, <a href="postconf.5.html#mailbox_transport">mailbox_transport</a>,
<a href="postconf.5.html#mailbox_command_maps">mailbox_command_maps</a>, <a href="postconf.5.html#mailbox_command">mailbox_command</a>, <a href="postconf.5.html#home_mailbox">home_mailbox</a>, <a href="postconf.5.html#mail_spool_directory">mail_spool_directory</a>,
<a href="postconf.5.html#fallback_transport_maps">fallback_transport_maps</a>, <a href="postconf.5.html#fallback_transport">fallback_transport</a> and <a href="postconf.5.html#luser_relay">luser_relay</a>.  </p>


</DD>

<DT><b><a name="mailbox_transport_maps">mailbox_transport_maps</a>
(default: empty)</b></DT><DD>

<p> Optional lookup tables with per-recipient message delivery
transports to use for <a href="local.8.html">local(8)</a> mailbox delivery, whether or not the
recipients are found in the UNIX passwd database. </p>

<p> The precedence of <a href="local.8.html">local(8)</a> delivery features from high to low
is: aliases, .forward files, <a href="postconf.5.html#mailbox_transport_maps">mailbox_transport_maps</a>, <a href="postconf.5.html#mailbox_transport">mailbox_transport</a>,
<a href="postconf.5.html#mailbox_command_maps">mailbox_command_maps</a>, <a href="postconf.5.html#mailbox_command">mailbox_command</a>, <a href="postconf.5.html#home_mailbox">home_mailbox</a>, <a href="postconf.5.html#mail_spool_directory">mail_spool_directory</a>,
<a href="postconf.5.html#fallback_transport_maps">fallback_transport_maps</a>, <a href="postconf.5.html#fallback_transport">fallback_transport</a> and <a href="postconf.5.html#luser_relay">luser_relay</a>.  </p>

<p> For safety reasons, this feature does not allow $number
substitutions in regular expression maps. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="mailq_path">mailq_path</a>
(default: see "postconf -d" output)</b></DT><DD>

<p>
Sendmail compatibility feature that specifies where the Postfix
<a href="mailq.1.html">mailq(1)</a> command is installed. This command can be used to
list the Postfix mail queue.
</p>


</DD>

<DT><b><a name="manpage_directory">manpage_directory</a>
(default: see "postconf -d" output)</b></DT><DD>

<p>
Where the Postfix manual pages are installed.
</p>


</DD>

<DT><b><a name="maps_rbl_domains">maps_rbl_domains</a>
(default: empty)</b></DT><DD>

<p>
Obsolete feature: use the <a href="postconf.5.html#reject_rbl_client">reject_rbl_client</a> feature instead.
</p>


</DD>

<DT><b><a name="maps_rbl_reject_code">maps_rbl_reject_code</a>
(default: 554)</b></DT><DD>

<p>
The numerical Postfix SMTP server response code when a remote SMTP
client request is blocked by the <a href="postconf.5.html#reject_rbl_client">reject_rbl_client</a>, <a href="postconf.5.html#reject_rhsbl_client">reject_rhsbl_client</a>,
<a href="postconf.5.html#reject_rhsbl_sender">reject_rhsbl_sender</a> or <a href="postconf.5.html#reject_rhsbl_recipient">reject_rhsbl_recipient</a> restriction.
</p>

<p>
Do not change this unless you have a complete understanding of <a href="http://tools.ietf.org/html/rfc821">RFC 821</a>.
</p>


</DD>

<DT><b><a name="masquerade_classes">masquerade_classes</a>
(default: envelope_sender, header_sender, header_recipient)</b></DT><DD>

<p>
What addresses are subject to address masquerading.
</p>

<p>
By default, address masquerading is limited to envelope sender
addresses, and to header sender and header recipient addresses.
This allows you to use address masquerading on a mail gateway while
still being able to forward mail to users on individual machines.
</p>

<p>
Specify zero or more of: envelope_sender, envelope_recipient,
header_sender, header_recipient
</p>


</DD>

<DT><b><a name="masquerade_domains">masquerade_domains</a>
(default: empty)</b></DT><DD>

<p>
Optional list of domains whose subdomain structure will be stripped
off in email addresses.
</p>

<p>
The list is processed left to right, and processing stops at the
first match.  Thus,
</p>

<blockquote>
<pre>
<a href="postconf.5.html#masquerade_domains">masquerade_domains</a> = foo.example.com example.com
</pre>
</blockquote>

<p>
strips "user@any.thing.foo.example.com" to "user@foo.example.com",
but strips "user@any.thing.else.example.com" to "user@example.com".
</p>

<p>
A domain name prefixed with ! means do not masquerade this domain
or its subdomains. Thus,
</p>

<blockquote>
<pre>
<a href="postconf.5.html#masquerade_domains">masquerade_domains</a> = !foo.example.com example.com
</pre>
</blockquote>

<p>
does not change "user@any.thing.foo.example.com" or "user@foo.example.com",
but strips "user@any.thing.else.example.com" to "user@example.com".
</p>

<p> Note: with Postfix version 2.2, message header address masquerading
happens only when message header address rewriting is enabled: </p>

<ul>

<li> The message is received with the Postfix <a href="sendmail.1.html">sendmail(1)</a> command,

<li> The message is received from a network client that matches
$<a href="postconf.5.html#local_header_rewrite_clients">local_header_rewrite_clients</a>,

<li> The message is received from the network, and the
<a href="postconf.5.html#remote_header_rewrite_domain">remote_header_rewrite_domain</a> parameter specifies a non-empty value.

</ul>

<p> To get the behavior before Postfix version 2.2, specify
"<a href="postconf.5.html#local_header_rewrite_clients">local_header_rewrite_clients</a> = static:all". </p>

<p>
Example:
</p>

<pre>
<a href="postconf.5.html#masquerade_domains">masquerade_domains</a> = $<a href="postconf.5.html#mydomain">mydomain</a>
</pre>


</DD>

<DT><b><a name="masquerade_exceptions">masquerade_exceptions</a>
(default: empty)</b></DT><DD>

<p>
Optional list of user names that are not subjected to address
masquerading, even when their address matches $<a href="postconf.5.html#masquerade_domains">masquerade_domains</a>.
</p>

<p>
By default, address masquerading makes no exceptions.
</p>

<p>
Specify a list of user names, "/file/name" or "<a href="DATABASE_README.html">type:table</a>" patterns,
separated by commas and/or whitespace. The list is matched left to
right, and the search stops on the first match. A "/file/name"
pattern is replaced
by its contents; a "<a href="DATABASE_README.html">type:table</a>" lookup table is matched when a name
matches a lookup key (the lookup result is ignored).  Continue long
lines by starting the next line with whitespace. Specify "!pattern"
to exclude a name from the list. The form "!/file/name" is supported
only in Postfix version 2.4 and later.  </p>

<p>
Examples:
</p>

<pre>
<a href="postconf.5.html#masquerade_exceptions">masquerade_exceptions</a> = root, mailer-daemon
<a href="postconf.5.html#masquerade_exceptions">masquerade_exceptions</a> = root
</pre>


</DD>

<DT><b><a name="max_idle">max_idle</a>
(default: 100s)</b></DT><DD>

<p>
The maximum amount of time that an idle Postfix daemon process waits
for an incoming connection before terminating voluntarily.  This
parameter
is ignored by the Postfix queue manager and by other long-lived
Postfix daemon processes.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>


</DD>

<DT><b><a name="max_use">max_use</a>
(default: 100)</b></DT><DD>

<p>
The maximal number of incoming connections that a Postfix daemon
process will service before terminating voluntarily.  This parameter
is ignored by the Postfix queue
manager and by other long-lived Postfix daemon processes.
</p>


</DD>

<DT><b><a name="maximal_backoff_time">maximal_backoff_time</a>
(default: 4000s)</b></DT><DD>

<p>
The maximal time between attempts to deliver a deferred message.
</p>

<p> This parameter should be set to a value greater than or equal
to $<a href="postconf.5.html#minimal_backoff_time">minimal_backoff_time</a>. See also $<a href="postconf.5.html#queue_run_delay">queue_run_delay</a>.  </p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>


</DD>

<DT><b><a name="maximal_queue_lifetime">maximal_queue_lifetime</a>
(default: 5d)</b></DT><DD>

<p>
The maximal time a message is queued before it is sent back as
undeliverable.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is d (days).
</p>

<p>
Specify 0 when mail delivery should be tried only once.
</p>


</DD>

<DT><b><a name="message_reject_characters">message_reject_characters</a>
(default: empty)</b></DT><DD>

<p> The set of characters that Postfix will reject in message
content.  The usual C-like escape sequences are recognized: <tt>\a
\b \f \n \r \t \v \<i>ddd</i></tt> (up to three octal digits) and
<tt>\\</tt>. </p>

<p> Example: </p>

<pre>
<a href="postconf.5.html#message_reject_characters">message_reject_characters</a> = \0
</pre>

<p> This feature is available in Postfix 2.3 and later.  </p>


</DD>

<DT><b><a name="message_size_limit">message_size_limit</a>
(default: 10240000)</b></DT><DD>

<p>
The maximal size in bytes of a message, including envelope information.
</p>


</DD>

<DT><b><a name="message_strip_characters">message_strip_characters</a>
(default: empty)</b></DT><DD>

<p> The set of characters that Postfix will remove from message
content.  The usual C-like escape sequences are recognized: <tt>\a
\b \f \n \r \t \v \<i>ddd</i></tt> (up to three octal digits) and
<tt>\\</tt>. </p>

<p> Example: </p>

<pre>
<a href="postconf.5.html#message_strip_characters">message_strip_characters</a> = \0
</pre>

<p> This feature is available in Postfix 2.3 and later.  </p>


</DD>

<DT><b><a name="milter_command_timeout">milter_command_timeout</a>
(default: 30s)</b></DT><DD>

<p> The time limit for sending an SMTP command to a Milter (mail
filter) application, and for receiving the response.  </p>

<p> Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). </p>

<p> Time units: s (seconds), m (minutes), h (hours), d (days), w
(weeks). The default time unit is s (seconds). </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="milter_connect_macros">milter_connect_macros</a>
(default: see postconf -n output)</b></DT><DD>

<p> The macros that are sent to Milter (mail filter) applications
after completion of an SMTP connection. See <a href="MILTER_README.html">MILTER_README</a>
for a list of available macro names and their meanings. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="milter_connect_timeout">milter_connect_timeout</a>
(default: 30s)</b></DT><DD>

<p> The time limit for connecting to a Milter (mail filter)
application, and for negotiating protocol options. </p>

<p> Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). </p>

<p> Time units: s (seconds), m (minutes), h (hours), d (days), w
(weeks). The default time unit is s (seconds). </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="milter_content_timeout">milter_content_timeout</a>
(default: 300s)</b></DT><DD>

<p> The time limit for sending message content to a Milter (mail
filter) application, and for receiving the response.  </p>

<p> Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). </p>

<p> Time units: s (seconds), m (minutes), h (hours), d (days), w
(weeks). The default time unit is s (seconds). </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="milter_data_macros">milter_data_macros</a>
(default: see postconf -n output)</b></DT><DD>

<p> The macros that are sent to version 4 or higher Milter (mail
filter) applications after the SMTP DATA command. See <a href="MILTER_README.html">MILTER_README</a>
for a list of available macro names and their meanings.  </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="milter_default_action">milter_default_action</a>
(default: tempfail)</b></DT><DD>

<p> The default action when a Milter (mail filter) application is
unavailable or mis-configured. Specify one of the following: </p>

<dl compact>

<dt>accept</dt> <dd>Proceed as if the mail filter was not present.
</dd>

<dt>reject</dt> <dd>Reject all further commands in this session
with a permanent status code.</dd>

<dt>tempfail</dt> <dd>Reject all further commands in this session
with a temporary status code. </dd>

</dl>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="milter_end_of_data_macros">milter_end_of_data_macros</a>
(default: see postconf -n output)</b></DT><DD>

<p> The macros that are sent to Milter (mail filter) applications
after the message end-of-data. See <a href="MILTER_README.html">MILTER_README</a> for a list of
available macro names and their meanings.  </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="milter_end_of_header_macros">milter_end_of_header_macros</a>
(default: see postconf -n output)</b></DT><DD>

<p> The macros that are sent to Milter (mail filter) applications
after the end of the message header. See <a href="MILTER_README.html">MILTER_README</a> for a list
of available macro names and their meanings.  </p>

<p> This feature is available in Postfix 2.5 and later. </p>


</DD>

<DT><b><a name="milter_helo_macros">milter_helo_macros</a>
(default: see postconf -n output)</b></DT><DD>

<p> The macros that are sent to Milter (mail filter) applications
after the SMTP HELO or EHLO command. See
<a href="MILTER_README.html">MILTER_README</a> for a list of available macro names and their meanings.
</p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="milter_macro_daemon_name">milter_macro_daemon_name</a>
(default: $<a href="postconf.5.html#myhostname">myhostname</a>)</b></DT><DD>

<p> The {daemon_name} macro value for Milter (mail filter) applications.
See <a href="MILTER_README.html">MILTER_README</a> for a list of available macro names and their
meanings.  </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="milter_macro_v">milter_macro_v</a>
(default: $<a href="postconf.5.html#mail_name">mail_name</a> $<a href="postconf.5.html#mail_version">mail_version</a>)</b></DT><DD>

<p> The {v} macro value for Milter (mail filter) applications.
See <a href="MILTER_README.html">MILTER_README</a> for a list of available macro names and their
meanings.  </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="milter_mail_macros">milter_mail_macros</a>
(default: see postconf -n output)</b></DT><DD>

<p> The macros that are sent to Milter (mail filter) applications
after the SMTP MAIL FROM command. See <a href="MILTER_README.html">MILTER_README</a>
for a list of available macro names and their meanings. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="milter_protocol">milter_protocol</a>
(default: 2)</b></DT><DD>

<p> The mail filter protocol version and optional protocol extensions
for communication with a Milter (mail filter) application. Postfix
sends this version number during the initial protocol handshake.
It should match the version number that is expected by the mail
filter application (or by its Milter library).  </p>

<p>Protocol versions: </p>

<dl compact>

<dt>2</dt> <dd>Use Sendmail 8 mail filter protocol version 2 (default
as of Sendmail version 8.11).</dd>

<dt>3</dt> <dd>Use Sendmail 8 mail filter protocol version 3.</dd>

<dt>4</dt> <dd>Use Sendmail 8 mail filter protocol version 4.</dd>

<dt>6</dt> <dd>Use Sendmail 8 mail filter protocol version 6 (default
as of Sendmail version 8.14).</dd>

</dl>

<p>Protocol extensions: </p>

<dl compact>

<dt>no_header_reply</dt> <dd> Specify this when the Milter application
will not reply for each individual message header.</dd>

</dl>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="milter_rcpt_macros">milter_rcpt_macros</a>
(default: see postconf -n output)</b></DT><DD>

<p> The macros that are sent to Milter (mail filter) applications
after the SMTP RCPT TO command. See <a href="MILTER_README.html">MILTER_README</a>
for a list of available macro names and their meanings. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="milter_unknown_command_macros">milter_unknown_command_macros</a>
(default: see postconf -n output)</b></DT><DD>

<p> The macros that are sent to version 3 or higher Milter (mail
filter) applications after an unknown SMTP command.  See <a href="MILTER_README.html">MILTER_README</a>
for a list of available macro names and their meanings.  </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="mime_boundary_length_limit">mime_boundary_length_limit</a>
(default: 2048)</b></DT><DD>

<p>
The maximal length of MIME multipart boundary strings. The MIME
processor is unable to distinguish between boundary strings that
do not differ in the first $<a href="postconf.5.html#mime_boundary_length_limit">mime_boundary_length_limit</a> characters.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>


</DD>

<DT><b><a name="mime_header_checks">mime_header_checks</a>
(default: $<a href="postconf.5.html#header_checks">header_checks</a>)</b></DT><DD>

<p>
Optional lookup tables for content inspection of MIME related
message headers, as described in the <a href="header_checks.5.html">header_checks(5)</a> manual page.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>


</DD>

<DT><b><a name="mime_nesting_limit">mime_nesting_limit</a>
(default: 100)</b></DT><DD>

<p>
The maximal recursion level that the MIME processor will handle.
Postfix refuses mail that is nested deeper than the specified limit.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>


</DD>

<DT><b><a name="minimal_backoff_time">minimal_backoff_time</a>
(default: 300s)</b></DT><DD>

<p>
The minimal time between attempts to deliver a deferred message;
prior to Postfix 2.4 the default value was 1000s.
</p>

<p>
This parameter also limits the time an unreachable destination is
kept in the short-term, in-memory, destination status cache.
</p>

<p> This parameter should be set greater than or equal to
$<a href="postconf.5.html#queue_run_delay">queue_run_delay</a>. See also $<a href="postconf.5.html#maximal_backoff_time">maximal_backoff_time</a>.  </p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>


</DD>

<DT><b><a name="multi_recipient_bounce_reject_code">multi_recipient_bounce_reject_code</a>
(default: 550)</b></DT><DD>

<p>
The numerical Postfix SMTP server response code when a remote SMTP
client request is blocked by the <a href="postconf.5.html#reject_multi_recipient_bounce">reject_multi_recipient_bounce</a>
restriction.
</p>

<p>
Do not change this unless you have a complete understanding of <a href="http://tools.ietf.org/html/rfc821">RFC 821</a>.
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>


</DD>

<DT><b><a name="mydestination">mydestination</a>
(default: $<a href="postconf.5.html#myhostname">myhostname</a>, localhost.$<a href="postconf.5.html#mydomain">mydomain</a>, localhost)</b></DT><DD>

<p> The list of domains that are delivered via the $<a href="postconf.5.html#local_transport">local_transport</a>
mail delivery transport. By default this is the Postfix <a href="local.8.html">local(8)</a>
delivery agent which looks up all recipients in /etc/passwd and
/etc/aliases. The SMTP server validates recipient addresses with
$<a href="postconf.5.html#local_recipient_maps">local_recipient_maps</a> and rejects non-existent recipients. See also
the <a href="ADDRESS_CLASS_README.html#local_domain_class">local domain</a> class in the <a href="ADDRESS_CLASS_README.html">ADDRESS_CLASS_README</a> file.
</p>

<p>
The default <a href="postconf.5.html#mydestination">mydestination</a> value specifies names for the local
machine only.  On a mail domain gateway, you should also include
$<a href="postconf.5.html#mydomain">mydomain</a>.
</p>

<p>
The $<a href="postconf.5.html#local_transport">local_transport</a> delivery method is also selected for mail
addressed to user@[the.net.work.address] of the mail system (the
IP addresses specified with the <a href="postconf.5.html#inet_interfaces">inet_interfaces</a> and <a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a>
parameters).
</p>

<p>
Warnings:
</p>

<ul>

<li><p>Do not specify the names of virtual domains - those domains
are specified elsewhere. See <a href="VIRTUAL_README.html">VIRTUAL_README</a> for more information. </p>

<li><p>Do not specify the names of domains that this machine is
backup MX host for. See <a href="STANDARD_CONFIGURATION_README.html">STANDARD_CONFIGURATION_README</a> for how to
set up backup MX hosts. </p>

<li><p>By default, the Postfix SMTP server rejects mail for recipients
not listed with the <a href="postconf.5.html#local_recipient_maps">local_recipient_maps</a> parameter.  See the
<a href="postconf.5.html">postconf(5)</a> manual for a description of the <a href="postconf.5.html#local_recipient_maps">local_recipient_maps</a>
and <a href="postconf.5.html#unknown_local_recipient_reject_code">unknown_local_recipient_reject_code</a> parameters. </p>

</ul>

<p>
Specify a list of host or domain names, "/file/name" or "<a href="DATABASE_README.html">type:table</a>"
patterns, separated by commas and/or whitespace. A "/file/name"
pattern is replaced by its contents; a "<a href="DATABASE_README.html">type:table</a>" lookup table
is matched when a name matches a lookup key (the lookup result is
ignored).  Continue long lines by starting the next line with
whitespace.  </p>

<p>
Examples:
</p>

<pre>
<a href="postconf.5.html#mydestination">mydestination</a> = $<a href="postconf.5.html#myhostname">myhostname</a>, localhost.$<a href="postconf.5.html#mydomain">mydomain</a> $<a href="postconf.5.html#mydomain">mydomain</a>
<a href="postconf.5.html#mydestination">mydestination</a> = $<a href="postconf.5.html#myhostname">myhostname</a>, localhost.$<a href="postconf.5.html#mydomain">mydomain</a> www.$<a href="postconf.5.html#mydomain">mydomain</a>, ftp.$<a href="postconf.5.html#mydomain">mydomain</a>
</pre>


</DD>

<DT><b><a name="mydomain">mydomain</a>
(default: see "postconf -d" output)</b></DT><DD>

<p>
The internet domain name of this mail system.  The default is to
use $<a href="postconf.5.html#myhostname">myhostname</a> minus the first component.  $<a href="postconf.5.html#mydomain">mydomain</a> is used as
a default value for many other configuration parameters.
</p>

<p>
Example:
</p>

<pre>
<a href="postconf.5.html#mydomain">mydomain</a> = domain.tld
</pre>


</DD>

<DT><b><a name="myhostname">myhostname</a>
(default: see "postconf -d" output)</b></DT><DD>

<p>
The internet hostname of this mail system. The default is to use
the fully-qualified domain name from gethostname(). $<a href="postconf.5.html#myhostname">myhostname</a> is
used as a default value for many other configuration parameters.
</p>

<p>
Example:
</p>

<pre>
<a href="postconf.5.html#myhostname">myhostname</a> = host.domain.tld
</pre>


</DD>

<DT><b><a name="mynetworks">mynetworks</a>
(default: see "postconf -d" output)</b></DT><DD>

<p>
The list of "trusted" SMTP clients that have more privileges than
"strangers".
</p>

<p>
In particular, "trusted" SMTP clients are allowed to relay mail
through Postfix.  See the <a href="postconf.5.html#smtpd_recipient_restrictions">smtpd_recipient_restrictions</a> parameter
description in the <a href="postconf.5.html">postconf(5)</a> manual.
</p>

<p>
You can specify the list of "trusted" network addresses by hand
or you can let Postfix do it for you (which is the default).
See the description of the <a href="postconf.5.html#mynetworks_style">mynetworks_style</a> parameter for more
information.
</p>

<p>
If you specify the <a href="postconf.5.html#mynetworks">mynetworks</a> list by hand,
Postfix ignores the <a href="postconf.5.html#mynetworks_style">mynetworks_style</a> setting.
</p>

<p> Specify a list of network addresses or network/netmask patterns,
separated by commas and/or whitespace. Continue long lines by
starting the next line with whitespace. </p>

<p> The netmask specifies the number of bits in the network part
of a host address.  You can also specify "/file/name" or "<a href="DATABASE_README.html">type:table</a>"
patterns.  A "/file/name" pattern is replaced by its contents; a
"<a href="DATABASE_README.html">type:table</a>" lookup table is matched when a table entry matches a
lookup string (the lookup result is ignored). </p>

<p> The list is matched left to right, and the search stops on the
first match.  Specify "!pattern" to exclude an address or network
block from the list. The form "!/file/name" is supported only
in Postfix version 2.4 and later. </p>

<p> Note: IP version 6 address information must be specified inside
<tt>[]</tt> in the <a href="postconf.5.html#mynetworks">mynetworks</a> value, and in files specified with
"/file/name".  IP version 6 addresses contain the ":" character,
and would otherwise be confused with a "<a href="DATABASE_README.html">type:table</a>" pattern.  </p>

<p> Examples:  </p>

<pre>
<a href="postconf.5.html#mynetworks">mynetworks</a> = 127.0.0.0/8 168.100.189.0/28
<a href="postconf.5.html#mynetworks">mynetworks</a> = !192.168.0.1, 192.168.0.0/28
<a href="postconf.5.html#mynetworks">mynetworks</a> = 127.0.0.0/8 168.100.189.0/28 [::1]/128 [2001:240:587::]/64
<a href="postconf.5.html#mynetworks">mynetworks</a> = $<a href="postconf.5.html#config_directory">config_directory</a>/mynetworks
<a href="postconf.5.html#mynetworks">mynetworks</a> = hash:/etc/postfix/network_table
</pre>


</DD>

<DT><b><a name="mynetworks_style">mynetworks_style</a>
(default: subnet)</b></DT><DD>

<p>
The method to generate the default value for the <a href="postconf.5.html#mynetworks">mynetworks</a> parameter.
This is the list of trusted networks for relay access control etc.
</p>

<ul>

<li><p>Specify "<a href="postconf.5.html#mynetworks_style">mynetworks_style</a> = host" when Postfix should
"trust" only the local machine. </p>

<li><p>Specify "<a href="postconf.5.html#mynetworks_style">mynetworks_style</a> = subnet" when Postfix
should "trust" SMTP clients in the same IP subnetworks as the local
machine.  On Linux, this works correctly only with interfaces
specified with the "ifconfig" command. </p>

<li><p>Specify "<a href="postconf.5.html#mynetworks_style">mynetworks_style</a> = class" when Postfix should
"trust" SMTP clients in the same IP class A/B/C networks as the
local machine.  Don't do this with a dialup site - it would cause
Postfix to "trust" your entire provider's network.  Instead, specify
an explicit <a href="postconf.5.html#mynetworks">mynetworks</a> list by hand, as described with the <a href="postconf.5.html#mynetworks">mynetworks</a>
configuration parameter. </p>

</ul>


</DD>

<DT><b><a name="myorigin">myorigin</a>
(default: $<a href="postconf.5.html#myhostname">myhostname</a>)</b></DT><DD>

<p>
The domain name that locally-posted mail appears to come
from, and that locally posted mail is delivered to. The default,
$<a href="postconf.5.html#myhostname">myhostname</a>, is adequate for small sites.  If you run a domain with
multiple machines, you should (1) change this to $<a href="postconf.5.html#mydomain">mydomain</a> and (2)
set up a domain-wide alias database that aliases each user to
user@that.users.mailhost.
</p>

<p>
Example:
</p>

<pre>
<a href="postconf.5.html#myorigin">myorigin</a> = $<a href="postconf.5.html#mydomain">mydomain</a>
</pre>


</DD>

<DT><b><a name="nested_header_checks">nested_header_checks</a>
(default: $<a href="postconf.5.html#header_checks">header_checks</a>)</b></DT><DD>

<p>
Optional lookup tables for content inspection of non-MIME message
headers in attached messages, as described in the <a href="header_checks.5.html">header_checks(5)</a>
manual page.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>


</DD>

<DT><b><a name="newaliases_path">newaliases_path</a>
(default: see "postconf -d" output)</b></DT><DD>

<p>
Sendmail compatibility feature that specifies the location of the
<a href="newaliases.1.html">newaliases(1)</a> command. This command can be used to rebuild the
<a href="local.8.html">local(8)</a> <a href="aliases.5.html">aliases(5)</a> database.
</p>


</DD>

<DT><b><a name="non_fqdn_reject_code">non_fqdn_reject_code</a>
(default: 504)</b></DT><DD>

<p>
The numerical Postfix SMTP server reply code when a client request
is rejected by the <a href="postconf.5.html#reject_non_fqdn_helo_hostname">reject_non_fqdn_helo_hostname</a>, <a href="postconf.5.html#reject_non_fqdn_sender">reject_non_fqdn_sender</a>
or <a href="postconf.5.html#reject_non_fqdn_recipient">reject_non_fqdn_recipient</a> restriction.
</p>


</DD>

<DT><b><a name="non_smtpd_milters">non_smtpd_milters</a>
(default: empty)</b></DT><DD>

<p> A list of Milter (mail filter) applications for new mail that
does not arrive via the Postfix <a href="smtpd.8.html">smtpd(8)</a> server. This includes local
submission via the <a href="sendmail.1.html">sendmail(1)</a> command line, new mail that arrives
via the Postfix <a href="qmqpd.8.html">qmqpd(8)</a> server, and old mail that is re-injected
into the queue with "postsuper -r".  See the <a href="MILTER_README.html">MILTER_README</a> document
for details.  </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="notify_classes">notify_classes</a>
(default: resource, software)</b></DT><DD>

<p>
The list of error classes that are reported to the postmaster. The
default is to report only the most serious problems. The paranoid
may wish to turn on the policy (UCE and mail relaying) and protocol
error (broken mail software) reports.
</p>

<p> NOTE: postmaster notifications may contain confidential information
such as SASL passwords or message content.  It is the system
administrator's responsibility to treat such information with care.
</p>

<p>
The error classes are:
</p>

<dl>

<dt><b>bounce</b> (also implies <b>2bounce</b>)</dt>

<dd>Send the postmaster copies of the headers of bounced mail, and
send transcripts of SMTP sessions when Postfix rejects mail. The
notification is sent to the address specified with the
<a href="postconf.5.html#bounce_notice_recipient">bounce_notice_recipient</a> configuration parameter (default: postmaster).
</dd>

<dt><b>2bounce</b></dt>

<dd>Send undeliverable bounced mail to the postmaster. The notification
is sent to the address specified with the <a href="postconf.5.html#2bounce_notice_recipient">2bounce_notice_recipient</a>
configuration parameter (default: postmaster). </dd>

<dt><b>delay</b></dt>

<dd>Send the postmaster copies of the headers of delayed mail. The
notification is sent to the address specified with the
<a href="postconf.5.html#delay_notice_recipient">delay_notice_recipient</a> configuration parameter (default: postmaster).
</dd>

<dt><b>policy</b></dt>

<dd>Send the postmaster a transcript of the SMTP session when a
client request was rejected because of (UCE) policy. The notification
is sent to the address specified with the <a href="postconf.5.html#error_notice_recipient">error_notice_recipient</a>
configuration parameter (default: postmaster).  </dd>

<dt><b>protocol</b></dt>

<dd>Send the postmaster a transcript of the SMTP session in case
of client or server protocol errors. The notification is sent to
the address specified with the <a href="postconf.5.html#error_notice_recipient">error_notice_recipient</a> configuration
parameter (default: postmaster). </dd>

<dt><b>resource</b></dt>

<dd>Inform the postmaster of mail not delivered due to resource
problems.  The notification is sent to the address specified with
the <a href="postconf.5.html#error_notice_recipient">error_notice_recipient</a> configuration parameter (default:
postmaster). </dd>

<dt><b>software</b></dt>

<dd>Inform the postmaster of mail not delivered due to software
problems.  The notification is sent to the address specified with
the <a href="postconf.5.html#error_notice_recipient">error_notice_recipient</a> configuration parameter (default:
postmaster). </dd>

</dl>

<p>
Examples:
</p>

<pre>
<a href="postconf.5.html#notify_classes">notify_classes</a> = bounce, delay, policy, protocol, resource, software
<a href="postconf.5.html#notify_classes">notify_classes</a> = 2bounce, resource, software
</pre>


</DD>

<DT><b><a name="owner_request_special">owner_request_special</a>
(default: yes)</b></DT><DD>

<p>
Give special treatment to owner-listname and listname-request
address localparts: don't split such addresses when the
<a href="postconf.5.html#recipient_delimiter">recipient_delimiter</a> is set to "-".  This feature is useful for
mailing lists.
</p>


</DD>

<DT><b><a name="parent_domain_matches_subdomains">parent_domain_matches_subdomains</a>
(default: see "postconf -d" output)</b></DT><DD>

<p>
What Postfix features match subdomains of "domain.tld" automatically,
instead of requiring an explicit ".domain.tld" pattern.  This is
planned backwards compatibility:  eventually, all Postfix features
are expected to require explicit ".domain.tld" style patterns when
you really want to match subdomains.
</p>


</DD>

<DT><b><a name="permit_mx_backup_networks">permit_mx_backup_networks</a>
(default: empty)</b></DT><DD>

<p>
Restrict the use of the <a href="postconf.5.html#permit_mx_backup">permit_mx_backup</a> SMTP access feature to
only domains whose primary MX hosts match the listed networks.
</p>


</DD>

<DT><b><a name="pickup_service_name">pickup_service_name</a>
(default: pickup)</b></DT><DD>

<p>
The name of the <a href="pickup.8.html">pickup(8)</a> service. This service picks up local mail
submissions from the Postfix <a href="QSHAPE_README.html#maildrop_queue">maildrop queue</a>.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>


</DD>

<DT><b><a name="plaintext_reject_code">plaintext_reject_code</a>
(default: 450)</b></DT><DD>

<p>
The numerical Postfix SMTP server response code when a request
is rejected by the <b><a href="postconf.5.html#reject_plaintext_session">reject_plaintext_session</a></b> restriction.
</p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="prepend_delivered_header">prepend_delivered_header</a>
(default: command, file, forward)</b></DT><DD>

<p> The message delivery contexts where the Postfix <a href="local.8.html">local(8)</a> delivery
agent prepends a Delivered-To:  message header with the address
that the mail was delivered to. This information is used for mail
delivery loop detection.  </p>

<p>
By default, the Postfix local delivery agent prepends a Delivered-To:
header when forwarding mail and when delivering to file (mailbox)
and command. Turning off the Delivered-To: header when forwarding
mail is not recommended.
</p>

<p>
Specify zero or more of <b>forward</b>, <b>file</b>, or <b>command</b>.
</p>

<p>
Example:
</p>

<pre>
<a href="postconf.5.html#prepend_delivered_header">prepend_delivered_header</a> = forward
</pre>


</DD>

<DT><b><a name="process_id">process_id</a>
(read-only)</b></DT><DD>

<p>
The process ID of a Postfix command or daemon process.
</p>


</DD>

<DT><b><a name="process_id_directory">process_id_directory</a>
(default: pid)</b></DT><DD>

<p>
The location of Postfix PID files relative to $<a href="postconf.5.html#queue_directory">queue_directory</a>.
This is a read-only parameter.
</p>


</DD>

<DT><b><a name="process_name">process_name</a>
(read-only)</b></DT><DD>

<p>
The process name of a Postfix command or daemon process.
</p>


</DD>

<DT><b><a name="propagate_unmatched_extensions">propagate_unmatched_extensions</a>
(default: canonical, virtual)</b></DT><DD>

<p>
What address lookup tables copy an address extension from the lookup
key to the lookup result.
</p>

<p>
For example, with a <a href="virtual.5.html">virtual(5)</a> mapping of "<i>joe@domain -&gt;
joe.user</i>", the address "<i>joe+foo@domain</i>" would rewrite
to "<i>joe.user+foo</i>".
</p>

<p>
Specify zero or more of <b>canonical</b>, <b>virtual</b>, <b>alias</b>,
<b>forward</b>, <b>include</b> or <b>generic</b>. These cause
address extension
propagation with <a href="canonical.5.html">canonical(5)</a>, <a href="virtual.5.html">virtual(5)</a>, and <a href="aliases.5.html">aliases(5)</a> maps,
with <a href="local.8.html">local(8)</a> .forward and :include: file lookups, and with <a href="smtp.8.html">smtp(8)</a>
generic maps, respectively.  </p>

<p>
Note: enabling this feature for types other than <b>canonical</b>
and <b>virtual</b> is likely to cause problems when mail is forwarded
to other sites, especially with mail that is sent to a mailing list
exploder address.
</p>

<p>
Examples:
</p>

<pre>
<a href="postconf.5.html#propagate_unmatched_extensions">propagate_unmatched_extensions</a> = canonical, virtual, alias,
        forward, include
<a href="postconf.5.html#propagate_unmatched_extensions">propagate_unmatched_extensions</a> = canonical, virtual
</pre>


</DD>

<DT><b><a name="proxy_interfaces">proxy_interfaces</a>
(default: empty)</b></DT><DD>

<p>
The network interface addresses that this mail system receives mail
on by way of a proxy or network address translation unit.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>

<p> You must specify your "outside" proxy/NAT addresses when your
system is a backup MX host for other domains, otherwise mail delivery
loops will happen when the primary MX host is down.  </p>

<p>
Example:
</p>

<pre>
<a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a> = 1.2.3.4
</pre>


</DD>

<DT><b><a name="proxy_read_maps">proxy_read_maps</a>
(default: see "postconf -d" output)</b></DT><DD>

<p>
The lookup tables that the <a href="proxymap.8.html">proxymap(8)</a> server is allowed to
access for the read-only service.
Table references that don't begin with <a href="proxymap.8.html">proxy</a>: are ignored.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>


</DD>

<DT><b><a name="proxy_write_maps">proxy_write_maps</a>
(default: see "postconf -d" output)</b></DT><DD>

<p> The lookup tables that the <a href="proxymap.8.html">proxymap(8)</a> server is allowed to
access for the read-write service. Postfix-owned local database
files should be stored under the Postfix-owned <a href="postconf.5.html#data_directory">data_directory</a>.
Table references that don't begin with <a href="proxymap.8.html">proxy</a>: are ignored.  </p>

<p>
This feature is available in Postfix 2.5 and later.
</p>


</DD>

<DT><b><a name="qmgr_clog_warn_time">qmgr_clog_warn_time</a>
(default: 300s)</b></DT><DD>

<p>
The minimal delay between warnings that a specific destination is
clogging up the Postfix <a href="QSHAPE_README.html#active_queue">active queue</a>. Specify 0 to disable.
</p>

<p>
This feature is enabled with the <a href="postconf.5.html#helpful_warnings">helpful_warnings</a> parameter.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>


</DD>

<DT><b><a name="qmgr_fudge_factor">qmgr_fudge_factor</a>
(default: 100)</b></DT><DD>

<p>
Obsolete feature: the percentage of delivery resources that a busy
mail system will use up for delivery of a large mailing  list
message.
</p>

<p>
This feature exists only in the <a href="qmgr.8.html">oqmgr(8)</a> old queue manager. The
current queue manager solves the problem in a better way.
</p>


</DD>

<DT><b><a name="qmgr_message_active_limit">qmgr_message_active_limit</a>
(default: 20000)</b></DT><DD>

<p>
The maximal number of messages in the <a href="QSHAPE_README.html#active_queue">active queue</a>.
</p>


</DD>

<DT><b><a name="qmgr_message_recipient_limit">qmgr_message_recipient_limit</a>
(default: 20000)</b></DT><DD>

<p> The maximal number of recipients held in memory by the Postfix
queue manager, and the maximal size of the size of the short-term,
in-memory "dead" destination status cache.  </p>


</DD>

<DT><b><a name="qmgr_message_recipient_minimum">qmgr_message_recipient_minimum</a>
(default: 10)</b></DT><DD>

<p>
The minimal number of in-memory recipients for any message. This
takes priority over any other in-memory recipient limits (i.e.,
the global <a href="postconf.5.html#qmgr_message_recipient_limit">qmgr_message_recipient_limit</a> and the per transport
_recipient_limit) if necessary. The minimum value allowed for this
parameter is 1.
</p>


</DD>

<DT><b><a name="qmqpd_authorized_clients">qmqpd_authorized_clients</a>
(default: empty)</b></DT><DD>

<p>
What clients are allowed to connect to the QMQP server port.
</p>

<p>
By default, no client is allowed to use the service. This is
because the QMQP server will relay mail to any destination.
</p>

<p>
Specify a list of client patterns. A list pattern specifies a host
name, a domain name, an internet address, or a network/mask pattern,
where the mask specifies the number of bits in the network part.
When a pattern specifies a file name, its contents are substituted
for the file name; when a pattern is a "<a href="DATABASE_README.html">type:table</a>" table specification,
table lookup is used instead.  </p>

<p>
Patterns are separated by whitespace and/or commas. In order to
reverse the result, precede a pattern with an
exclamation point (!). The form "!/file/name" is supported only
in Postfix version 2.4 and later.
</p>

<p>
Example:
</p>

<pre>
<a href="postconf.5.html#qmqpd_authorized_clients">qmqpd_authorized_clients</a> = !192.168.0.1, 192.168.0.0/24
</pre>


</DD>

<DT><b><a name="qmqpd_client_port_logging">qmqpd_client_port_logging</a>
(default: no)</b></DT><DD>

<p> Enable logging of the remote QMQP client port in addition to
the hostname and IP address. The logging format is "host[address]:port".
</p>

<p> This feature is available in Postfix 2.5 and later. </p>


</DD>

<DT><b><a name="qmqpd_error_delay">qmqpd_error_delay</a>
(default: 1s)</b></DT><DD>

<p>
How long the QMQP server will pause before sending a negative reply
to the client. The purpose is to slow down confused or malicious
clients.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>


</DD>

<DT><b><a name="qmqpd_timeout">qmqpd_timeout</a>
(default: 300s)</b></DT><DD>

<p>
The time limit for sending or receiving information over the network.
If a read or write operation blocks for more than $<a href="postconf.5.html#qmqpd_timeout">qmqpd_timeout</a>
seconds the QMQP server gives up and disconnects.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>


</DD>

<DT><b><a name="queue_directory">queue_directory</a>
(default: see "postconf -d" output)</b></DT><DD>

<p>
The location of the Postfix top-level queue directory. This is the
root directory of Postfix daemon processes that run chrooted.
</p>


</DD>

<DT><b><a name="queue_file_attribute_count_limit">queue_file_attribute_count_limit</a>
(default: 100)</b></DT><DD>

<p>
The maximal number of (name=value) attributes that may be stored
in a Postfix queue file. The limit is enforced by the <a href="cleanup.8.html">cleanup(8)</a>
server.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>


</DD>

<DT><b><a name="queue_minfree">queue_minfree</a>
(default: 0)</b></DT><DD>

<p>
The minimal amount of free space in bytes in the queue file system
that is needed to receive mail.  This is currently used by the SMTP
server to decide if it will accept any mail at all.
</p>

<p>
By default, the Postfix version 2.1 SMTP server rejects MAIL FROM commands
when the amount of free space is less than 1.5*$<a href="postconf.5.html#message_size_limit">message_size_limit</a>.
To specify a higher minimum free space limit, specify a <a href="postconf.5.html#queue_minfree">queue_minfree</a>
value that is at least 1.5*$<a href="postconf.5.html#message_size_limit">message_size_limit</a>.
</p>

<p>
With Postfix versions 2.0 and earlier, a <a href="postconf.5.html#queue_minfree">queue_minfree</a> value of
zero means there is no minimum required amount of free space.
</p>


</DD>

<DT><b><a name="queue_run_delay">queue_run_delay</a>
(default: 300s)</b></DT><DD>

<p>
The time between <a href="QSHAPE_README.html#deferred_queue">deferred queue</a> scans by the queue manager;
prior to Postfix 2.4 the default value was 1000s.
</p>

<p> This parameter should be set less than or equal to
$<a href="postconf.5.html#minimal_backoff_time">minimal_backoff_time</a>. See also $<a href="postconf.5.html#maximal_backoff_time">maximal_backoff_time</a>.  </p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>


</DD>

<DT><b><a name="queue_service_name">queue_service_name</a>
(default: qmgr)</b></DT><DD>

<p>
The name of the <a href="qmgr.8.html">qmgr(8)</a> service. This service manages the Postfix
queue and schedules delivery requests.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>


</DD>

<DT><b><a name="rbl_reply_maps">rbl_reply_maps</a>
(default: empty)</b></DT><DD>

<p>
Optional lookup tables with RBL response templates. The tables are
indexed by the RBL domain name. By default, Postfix uses the default
template as specified with the <a href="postconf.5.html#default_rbl_reply">default_rbl_reply</a> configuration
parameter. See there for a discussion of the syntax of RBL reply
templates.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>


</DD>

<DT><b><a name="readme_directory">readme_directory</a>
(default: see "postconf -d" output)</b></DT><DD>

<p>
The location of Postfix README files that describe how to build,
configure or operate a specific Postfix subsystem or feature.
</p>


</DD>

<DT><b><a name="receive_override_options">receive_override_options</a>
(default: empty)</b></DT><DD>

<p> Enable or disable recipient validation, built-in content
filtering, or address mapping. Typically, these are specified in
<a href="master.5.html">master.cf</a> as command-line arguments for the <a href="smtpd.8.html">smtpd(8)</a>, <a href="qmqpd.8.html">qmqpd(8)</a> or
<a href="pickup.8.html">pickup(8)</a> daemons. </p>

<p> Specify zero or more of the following options.  The options
override <a href="postconf.5.html">main.cf</a> settings and are either implemented by <a href="smtpd.8.html">smtpd(8)</a>,
<a href="qmqpd.8.html">qmqpd(8)</a>, or <a href="pickup.8.html">pickup(8)</a> themselves, or they are forwarded to the
cleanup server.  </p>

<dl>

<dt><b><a name="no_unknown_recipient_checks">no_unknown_recipient_checks</a></b></dt>

<dd>Do not try to reject unknown recipients (SMTP server only).
This is typically specified AFTER an external content filter.
</dd>

<dt><b><a name="no_address_mappings">no_address_mappings</a></b></dt>

<dd>Disable canonical address mapping, virtual alias map expansion,
address masquerading, and automatic BCC (blind carbon-copy)
recipients. This is typically specified BEFORE an external content
filter. </dd>

<dt><b><a name="no_header_body_checks">no_header_body_checks</a></b></dt>

<dd>Disable header/body_checks. This is typically specified AFTER
an external content filter. </dd>

<dt><b><a name="no_milters">no_milters</a></b></dt>

<dd>Disable Milter (mail filter) applications. This is typically
specified AFTER an external content filter. </dd>

</dl>

<p>
Note: when the "BEFORE content filter" <a href="postconf.5.html#receive_override_options">receive_override_options</a>
setting is specified in the <a href="postconf.5.html">main.cf</a> file, specify the "AFTER content
filter" <a href="postconf.5.html#receive_override_options">receive_override_options</a> setting in <a href="master.5.html">master.cf</a> (and vice
versa).
</p>

<p>
Examples:
</p>

<pre>
<a href="postconf.5.html#receive_override_options">receive_override_options</a> =
    <a href="postconf.5.html#no_unknown_recipient_checks">no_unknown_recipient_checks</a>, <a href="postconf.5.html#no_header_body_checks">no_header_body_checks</a>
<a href="postconf.5.html#receive_override_options">receive_override_options</a> = <a href="postconf.5.html#no_address_mappings">no_address_mappings</a>
</pre>

<p>
This feature is available in Postfix 2.1 and later.
</p>


</DD>

<DT><b><a name="recipient_bcc_maps">recipient_bcc_maps</a>
(default: empty)</b></DT><DD>

<p>
Optional BCC (blind carbon-copy) address lookup tables, indexed by
recipient address.  The BCC address (multiple results are not
supported) is added when mail enters from outside of Postfix.
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>

<p>
The table search order is as follows:
</p>

<ul>

<li> Look up the "user+extension@domain.tld" address including the
optional address extension.

<li> Look up the "user@domain.tld" address without the optional
address extension.

<li> Look up the "user+extension" address local part when the
recipient domain equals $<a href="postconf.5.html#myorigin">myorigin</a>, $<a href="postconf.5.html#mydestination">mydestination</a>, $<a href="postconf.5.html#inet_interfaces">inet_interfaces</a>
or $<a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a>.

<li> Look up the "user" address local part when the recipient domain
equals $<a href="postconf.5.html#myorigin">myorigin</a>, $<a href="postconf.5.html#mydestination">mydestination</a>, $<a href="postconf.5.html#inet_interfaces">inet_interfaces</a> or $<a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a>.

<li> Look up the "@domain.tld" part.

</ul>

<p>
Specify the types and names of databases to use.  After change,
run "<b>postmap /etc/postfix/recipient_bcc</b>".
</p>

<p>
Note: if mail to the BCC address bounces it will be returned to
the sender.
</p>

<p> Note: automatic BCC recipients are produced only for new mail.
To avoid mailer loops, automatic BCC recipients are not generated
for mail that Postfix forwards internally, nor for mail that Postfix
generates itself. </p>

<p>
Example:
</p>

<pre>
<a href="postconf.5.html#recipient_bcc_maps">recipient_bcc_maps</a> = hash:/etc/postfix/recipient_bcc
</pre>


</DD>

<DT><b><a name="recipient_canonical_classes">recipient_canonical_classes</a>
(default: envelope_recipient, header_recipient)</b></DT><DD>

<p> What addresses are subject to <a href="postconf.5.html#recipient_canonical_maps">recipient_canonical_maps</a> address
mapping.  By default, <a href="postconf.5.html#recipient_canonical_maps">recipient_canonical_maps</a> address mapping is
applied to envelope recipient addresses, and to header recipient
addresses.  </p>

<p> Specify one or more of: envelope_recipient, header_recipient
</p>

<p> This feature is available in Postfix 2.2 and later. </p>


</DD>

<DT><b><a name="recipient_canonical_maps">recipient_canonical_maps</a>
(default: empty)</b></DT><DD>

<p>
Optional address mapping lookup tables for envelope and header
recipient addresses.
The table format and lookups are documented in <a href="canonical.5.html">canonical(5)</a>.
</p>

<p>
Note: $<a href="postconf.5.html#recipient_canonical_maps">recipient_canonical_maps</a> is processed before $<a href="postconf.5.html#canonical_maps">canonical_maps</a>.
</p>

<p>
Example:
</p>

<pre>
<a href="postconf.5.html#recipient_canonical_maps">recipient_canonical_maps</a> = hash:/etc/postfix/recipient_canonical
</pre>


</DD>

<DT><b><a name="recipient_delimiter">recipient_delimiter</a>
(default: empty)</b></DT><DD>

<p>
The separator between user names and address extensions (user+foo).
See <a href="canonical.5.html">canonical(5)</a>, <a href="local.8.html">local(8)</a>, <a href="relocated.5.html">relocated(5)</a> and <a href="virtual.5.html">virtual(5)</a> for the
effects this has on aliases, canonical, virtual, relocated and
on .forward file lookups.  Basically, the software tries user+foo
and .forward+foo before trying user and .forward.
</p>

<p>
Example:
</p>

<pre>
<a href="postconf.5.html#recipient_delimiter">recipient_delimiter</a> = +
</pre>


</DD>

<DT><b><a name="reject_code">reject_code</a>
(default: 554)</b></DT><DD>

<p>
The numerical Postfix SMTP server response code when a remote SMTP
client request is rejected by the "reject" restriction.
</p>

<p>
Do not change this unless you have a complete understanding of <a href="http://tools.ietf.org/html/rfc821">RFC 821</a>.
</p>


</DD>

<DT><b><a name="relay_clientcerts">relay_clientcerts</a>
(default: empty)</b></DT><DD>

<p> List of tables with remote SMTP client-certificate fingerprints
for which the Postfix SMTP server will allow access with the
<a href="postconf.5.html#permit_tls_clientcerts">permit_tls_clientcerts</a> feature.
The fingerprint digest algorithm is configurable via the
<a href="postconf.5.html#smtpd_tls_fingerprint_digest">smtpd_tls_fingerprint_digest</a> parameter (hard-coded as md5 prior to
Postfix version 2.5).  </p>

<p> Postfix lookup tables are in the form of (key, value) pairs.
Since we only need the key, the value can be chosen freely, e.g.
the name of the user or host:
D7:04:2F:A7:0B:8C:A5:21:FA:31:77:E1:41:8A:EE:80 lutzpc.at.home </p>

<p> Example: </p>

<pre>
<a href="postconf.5.html#relay_clientcerts">relay_clientcerts</a> = hash:/etc/postfix/relay_clientcerts
</pre>

<p>For more fine-grained control, use <a href="postconf.5.html#check_ccert_access">check_ccert_access</a> to select
an appropriate <a href="access.5.html">access(5)</a> policy for each client.
See <a href="RESTRICTION_CLASS_README.html">RESTRICTION_CLASS_README</a>.</p>

<p>This feature is available with Postfix version 2.2.</p>


</DD>

<DT><b><a name="relay_destination_concurrency_limit">relay_destination_concurrency_limit</a>
(default: $<a href="postconf.5.html#default_destination_concurrency_limit">default_destination_concurrency_limit</a>)</b></DT><DD>

<p> The maximal number of parallel deliveries to the same destination
via the relay message delivery transport. This limit is enforced
by the queue manager. The message delivery transport name is the
first field in the entry in the <a href="master.5.html">master.cf</a> file.  </p>

<p> This feature is available in Postfix 2.0 and later. </p>


</DD>

<DT><b><a name="relay_destination_recipient_limit">relay_destination_recipient_limit</a>
(default: $<a href="postconf.5.html#default_destination_recipient_limit">default_destination_recipient_limit</a>)</b></DT><DD>

<p> The maximal number of recipients per delivery via the relay
message delivery transport. This limit is enforced by the queue
manager. The message delivery transport name is the first field in
the entry in the <a href="master.5.html">master.cf</a> file.  </p>

<p> Setting this parameter to a value of 1 changes the meaning of
<a href="postconf.5.html#relay_destination_concurrency_limit">relay_destination_concurrency_limit</a> from concurrency per domain
into concurrency per recipient.  </p>

<p> This feature is available in Postfix 2.0 and later. </p>


</DD>

<DT><b><a name="relay_domains">relay_domains</a>
(default: $<a href="postconf.5.html#mydestination">mydestination</a>)</b></DT><DD>

<p> What destination domains (and subdomains thereof) this system
will relay mail to. Subdomain matching is controlled with the
<a href="postconf.5.html#parent_domain_matches_subdomains">parent_domain_matches_subdomains</a> parameter. For details about how
the <a href="postconf.5.html#relay_domains">relay_domains</a> value is used, see the description of the
<a href="postconf.5.html#permit_auth_destination">permit_auth_destination</a> and <a href="postconf.5.html#reject_unauth_destination">reject_unauth_destination</a> SMTP recipient
restrictions.  </p>

<p> Domains that match $<a href="postconf.5.html#relay_domains">relay_domains</a> are delivered with the
$<a href="postconf.5.html#relay_transport">relay_transport</a> mail delivery transport. The SMTP server validates
recipient addresses with $<a href="postconf.5.html#relay_recipient_maps">relay_recipient_maps</a> and rejects non-existent
recipients. See also the <a href="ADDRESS_CLASS_README.html#relay_domain_class">relay domains</a> address class in the
<a href="ADDRESS_CLASS_README.html">ADDRESS_CLASS_README</a> file.  </p>

<p> Note: Postfix will not automatically forward mail for domains
that list this system as their primary or backup MX host. See the
<a href="postconf.5.html#permit_mx_backup">permit_mx_backup</a> restriction in the <a href="postconf.5.html">postconf(5)</a> manual page.  </p>

<p> Specify a list of host or domain names, "/file/name" patterns
or "<a href="DATABASE_README.html">type:table</a>" lookup tables, separated by commas and/or whitespace.
Continue long lines by starting the next line with whitespace. A
"/file/name" pattern is replaced by its contents; a "<a href="DATABASE_README.html">type:table</a>"
lookup table is matched when a (parent) domain appears as lookup
key. Specify "!pattern" to exclude a domain from the list. The form
"!/file/name" is supported only in Postfix version 2.4 and later.
</p>


</DD>

<DT><b><a name="relay_domains_reject_code">relay_domains_reject_code</a>
(default: 554)</b></DT><DD>

<p>
The numerical Postfix SMTP server response code when a client
request is rejected by the <a href="postconf.5.html#reject_unauth_destination">reject_unauth_destination</a> recipient
restriction.
</p>

<p>
Do not change this unless you have a complete understanding of <a href="http://tools.ietf.org/html/rfc821">RFC 821</a>.
</p>


</DD>

<DT><b><a name="relay_recipient_maps">relay_recipient_maps</a>
(default: empty)</b></DT><DD>

<p> Optional lookup tables with all valid addresses in the domains
that match $<a href="postconf.5.html#relay_domains">relay_domains</a>. Specify @domain as a wild-card for
domains that have no valid recipient list, and become a source of
backscatter mail: Postfix accepts spam for non-existent recipients
and then floods innocent people with undeliverable mail.  Technically,
tables
listed with $<a href="postconf.5.html#relay_recipient_maps">relay_recipient_maps</a> are used as lists: Postfix needs
to know only if a lookup string is found or not, but it does not
use the result from table lookup.  </p>

<p>
If this parameter is non-empty, then the Postfix SMTP server will reject
mail to unknown relay users. This feature is off by default.
</p>

<p>
See also the <a href="ADDRESS_CLASS_README.html#relay_domain_class">relay domains</a> address class in the <a href="ADDRESS_CLASS_README.html">ADDRESS_CLASS_README</a>
file.
</p>

<p>
Example:
</p>

<pre>
<a href="postconf.5.html#relay_recipient_maps">relay_recipient_maps</a> = hash:/etc/postfix/relay_recipients
</pre>

<p>
This feature is available in Postfix 2.0 and later.
</p>


</DD>

<DT><b><a name="relay_transport">relay_transport</a>
(default: relay)</b></DT><DD>

<p>
The default mail delivery transport and next-hop destination for
remote delivery to domains listed with $<a href="postconf.5.html#relay_domains">relay_domains</a>. In order of
decreasing precedence, the nexthop destination is taken from
$<a href="postconf.5.html#relay_transport">relay_transport</a>, $<a href="postconf.5.html#sender_dependent_relayhost_maps">sender_dependent_relayhost_maps</a>, $<a href="postconf.5.html#relayhost">relayhost</a>, or
from the recipient domain. This information can be overruled with
the <a href="transport.5.html">transport(5)</a> table.
</p>

<p>
Specify a string of the form <i>transport:nexthop</i>, where <i>transport</i>
is the name of a mail delivery transport defined in <a href="master.5.html">master.cf</a>.
The <i>:nexthop</i> part is optional.  For more details see the
<a href="transport.5.html">transport(5)</a> manual page.
</p>

<p>
See also the <a href="ADDRESS_CLASS_README.html#relay_domain_class">relay domains</a> address class in the <a href="ADDRESS_CLASS_README.html">ADDRESS_CLASS_README</a>
file.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>


</DD>

<DT><b><a name="relayhost">relayhost</a>
(default: empty)</b></DT><DD>

<p>
The next-hop destination of non-local mail; overrides non-local
domains in recipient addresses. This information is overruled with
<a href="postconf.5.html#relay_transport">relay_transport</a>, <a href="postconf.5.html#default_transport">default_transport</a>, <a href="postconf.5.html#sender_dependent_relayhost_maps">sender_dependent_relayhost_maps</a>
and with the <a href="transport.5.html">transport(5)</a> table.
</p>

<p>
On an intranet, specify the organizational domain name. If your
internal DNS uses no MX records, specify the name of the intranet
gateway host instead.
</p>

<p>
In the case of SMTP, specify a domain name, hostname, hostname:port,
[hostname]:port, [hostaddress] or [hostaddress]:port. The form
[hostname] turns off MX lookups.
</p>

<p>
If you're connected via UUCP, see the <a href="UUCP_README.html">UUCP_README</a> file for useful
information.
</p>

<p>
Examples:
</p>

<pre>
<a href="postconf.5.html#relayhost">relayhost</a> = $<a href="postconf.5.html#mydomain">mydomain</a>
<a href="postconf.5.html#relayhost">relayhost</a> = [gateway.my.domain]
<a href="postconf.5.html#relayhost">relayhost</a> = uucphost
<a href="postconf.5.html#relayhost">relayhost</a> = [an.ip.add.ress]
</pre>


</DD>

<DT><b><a name="relocated_maps">relocated_maps</a>
(default: empty)</b></DT><DD>

<p>
Optional lookup tables with new contact information for users or
domains that no longer exist.  The table format and lookups are
documented in <a href="relocated.5.html">relocated(5)</a>.
</p>

<p>
If you use this feature, run "<b>postmap /etc/postfix/relocated</b>" to
build the necessary DBM or DB file after change, then "<b>postfix
reload</b>" to make the changes visible.
</p>

<p>
Examples:
</p>

<pre>
<a href="postconf.5.html#relocated_maps">relocated_maps</a> = dbm:/etc/postfix/relocated
<a href="postconf.5.html#relocated_maps">relocated_maps</a> = hash:/etc/postfix/relocated
</pre>


</DD>

<DT><b><a name="remote_header_rewrite_domain">remote_header_rewrite_domain</a>
(default: empty)</b></DT><DD>

<p> Don't rewrite message headers from remote clients at all when
this parameter is empty; otherwise, rewrite message headers and
append the specified domain name to incomplete addresses.  The
<a href="postconf.5.html#local_header_rewrite_clients">local_header_rewrite_clients</a> parameter controls what clients Postfix
considers local. </p>

<p> Examples:  </p>

<p> The safe setting: append "domain.invalid" to incomplete header
addresses from remote SMTP clients, so that those addresses cannot
be confused with local addresses. </p>

<blockquote>
<pre>
<a href="postconf.5.html#remote_header_rewrite_domain">remote_header_rewrite_domain</a> = domain.invalid
</pre>
</blockquote>

<p> The default, purist, setting: don't rewrite headers from remote
clients at all. </p>

<blockquote>
<pre>
<a href="postconf.5.html#remote_header_rewrite_domain">remote_header_rewrite_domain</a> =
</pre>
</blockquote>


</DD>

<DT><b><a name="require_home_directory">require_home_directory</a>
(default: no)</b></DT><DD>

<p>
Whether or not a <a href="local.8.html">local(8)</a> recipient's home directory must exist
before mail delivery is attempted. By default this test is disabled.
It can be useful for environments that import home directories to
the mail server (NOT RECOMMENDED).
</p>


</DD>

<DT><b><a name="resolve_dequoted_address">resolve_dequoted_address</a>
(default: yes)</b></DT><DD>

<p> Resolve a recipient address safely instead of correctly, by
looking inside quotes.  </p>

<p> By default, the Postfix address resolver does not quote the
address localpart as per <a href="http://tools.ietf.org/html/rfc822">RFC 822</a>, so that additional @ or % or !
operators remain visible. This behavior is safe but it is also
technically incorrect.  </p>

<p> If you specify "<a href="postconf.5.html#resolve_dequoted_address">resolve_dequoted_address</a> = no", then
the Postfix
resolver will not know about additional @ etc. operators in the
address localpart. This opens opportunities for obscure mail relay
attacks with user@domain@domain addresses when Postfix provides
backup MX service for Sendmail systems.  </p>


</DD>

<DT><b><a name="resolve_null_domain">resolve_null_domain</a>
(default: no)</b></DT><DD>

<p> Resolve an address that ends in the "@" null domain as if the
local hostname were specified, instead of rejecting the address as
invalid.  </p>

<p> This feature is available in Postfix 2.1 and later.
Earlier versions always resolve the null domain as the local
hostname.  </p>

<p> The Postfix SMTP server uses this feature to reject mail from
or to addresses that end in the "@" null domain, and from addresses
that rewrite into a form that ends in the "@" null domain.  </p>


</DD>

<DT><b><a name="resolve_numeric_domain">resolve_numeric_domain</a>
(default: no)</b></DT><DD>

<p> Resolve "user@ipaddress" as "user@[ipaddress]", instead of
rejecting the address as invalid.  </p>

<p> This feature is available in Postfix 2.3 and later.


</DD>

<DT><b><a name="rewrite_service_name">rewrite_service_name</a>
(default: rewrite)</b></DT><DD>

<p>
The name of the address rewriting service. This service rewrites
addresses to standard form and resolves them to a (delivery method,
next-hop host, recipient) triple.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>


</DD>

<DT><b><a name="sample_directory">sample_directory</a>
(default: /etc/postfix)</b></DT><DD>

<p>
The name of the directory with example Postfix configuration files.
</p>


</DD>

<DT><b><a name="send_cyrus_sasl_authzid">send_cyrus_sasl_authzid</a>
(default: no)</b></DT><DD>

<p> When authenticating to a remote SMTP or LMTP server with the
default setting "no", send no SASL authoriZation ID (authzid); send
only the SASL authentiCation ID (authcid) plus the authcid's password.
</p>

<p> The non-default setting "yes" enables the behavior of older
Postfix versions.  These always send a SASL authzid that is equal
to the SASL authcid, but this causes inter-operability problems
with some SMTP servers. </p>

<p> This feature is available in Postfix 2.4.4 and later. </p>


</DD>

<DT><b><a name="sender_based_routing">sender_based_routing</a>
(default: no)</b></DT><DD>

<p>
This parameter should not be used. It was replaced by <a href="postconf.5.html#sender_dependent_relayhost_maps">sender_dependent_relayhost_maps</a>
in Postfix version 2.3.
</p>


</DD>

<DT><b><a name="sender_bcc_maps">sender_bcc_maps</a>
(default: empty)</b></DT><DD>

<p> Optional BCC (blind carbon-copy) address lookup tables, indexed
by sender address.  The BCC address (multiple results are not
supported) is added when mail enters from outside of Postfix.  </p>

<p>
This feature is available in Postfix 2.1 and later.
</p>

<p>
The table search order is as follows:
</p>

<ul>

<li> Look up the "user+extension@domain.tld" address including the
optional address extension.

<li> Look up the "user@domain.tld" address without the optional
address extension.

<li> Look up the "user+extension" address local part when the
sender domain equals $<a href="postconf.5.html#myorigin">myorigin</a>, $<a href="postconf.5.html#mydestination">mydestination</a>, $<a href="postconf.5.html#inet_interfaces">inet_interfaces</a>
or $<a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a>.

<li> Look up the "user" address local part when the sender domain
equals $<a href="postconf.5.html#myorigin">myorigin</a>, $<a href="postconf.5.html#mydestination">mydestination</a>, $<a href="postconf.5.html#inet_interfaces">inet_interfaces</a> or $<a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a>.

<li> Look up the "@domain.tld" part.

</ul>

<p>
Specify the types and names of databases to use.  After change,
run "<b>postmap /etc/postfix/sender_bcc</b>".
</p>

<p>
Note: if mail to the BCC address bounces it will be returned to
the sender.
</p>

<p> Note: automatic BCC recipients are produced only for new mail.
To avoid mailer loops, automatic BCC recipients are not generated
for mail that Postfix forwards internally, nor for mail that Postfix
generates itself. </p>

<p>
Example:
</p>

<pre>
<a href="postconf.5.html#sender_bcc_maps">sender_bcc_maps</a> = hash:/etc/postfix/sender_bcc
</pre>


</DD>

<DT><b><a name="sender_canonical_classes">sender_canonical_classes</a>
(default: envelope_sender, header_sender)</b></DT><DD>

<p> What addresses are subject to <a href="postconf.5.html#sender_canonical_maps">sender_canonical_maps</a> address
mapping.  By default, <a href="postconf.5.html#sender_canonical_maps">sender_canonical_maps</a> address mapping is
applied to envelope sender addresses, and to header sender addresses.
</p>

<p> Specify one or more of: envelope_sender, header_sender </p>

<p> This feature is available in Postfix 2.2 and later. </p>


</DD>

<DT><b><a name="sender_canonical_maps">sender_canonical_maps</a>
(default: empty)</b></DT><DD>

<p>
Optional address mapping lookup tables for envelope and header
sender addresses.
The table format and lookups are documented in <a href="canonical.5.html">canonical(5)</a>.
</p>

<p>
Example: you want to rewrite the SENDER address "user@ugly.domain"
to "user@pretty.domain", while still being able to send mail to
the RECIPIENT address "user@ugly.domain".
</p>

<p>
Note: $<a href="postconf.5.html#sender_canonical_maps">sender_canonical_maps</a> is processed before $<a href="postconf.5.html#canonical_maps">canonical_maps</a>.
</p>

<p>
Example:
</p>

<pre>
<a href="postconf.5.html#sender_canonical_maps">sender_canonical_maps</a> = hash:/etc/postfix/sender_canonical
</pre>


</DD>

<DT><b><a name="sender_dependent_relayhost_maps">sender_dependent_relayhost_maps</a>
(default: empty)</b></DT><DD>

<p> A sender-dependent override for the global <a href="postconf.5.html#relayhost">relayhost</a> parameter
setting. The tables are searched by the envelope sender address and
@domain. This information is overruled with <a href="postconf.5.html#relay_transport">relay_transport</a>,
<a href="postconf.5.html#default_transport">default_transport</a> and with the <a href="transport.5.html">transport(5)</a> table. </p>

<p> For safety reasons, this feature does not allow $number
substitutions in regular expression maps. </p>

<p>
This feature is available in Postfix 2.3 and later.
</p>


</DD>

<DT><b><a name="sendmail_path">sendmail_path</a>
(default: see "postconf -d" output)</b></DT><DD>

<p>
A Sendmail compatibility feature that specifies the location of
the Postfix <a href="sendmail.1.html">sendmail(1)</a> command. This command can be used to
submit mail into the Postfix queue.
</p>


</DD>

<DT><b><a name="service_throttle_time">service_throttle_time</a>
(default: 60s)</b></DT><DD>

<p>
How long the Postfix <a href="master.8.html">master(8)</a> waits before forking a server that
appears to be malfunctioning.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>


</DD>

<DT><b><a name="setgid_group">setgid_group</a>
(default: postdrop)</b></DT><DD>

<p>
The group ownership of set-gid Postfix commands and of group-writable
Postfix directories. When this parameter value is changed you need
to re-run "<b>postfix set-permissions</b>" (with Postfix version 2.0 and
earlier: "<b>/etc/postfix/post-install set-permissions</b>".
</p>


</DD>

<DT><b><a name="show_user_unknown_table_name">show_user_unknown_table_name</a>
(default: yes)</b></DT><DD>

<p>
Display the name of the recipient table in the "User unknown"
responses.  The extra detail makes trouble shooting easier but also
reveals information that is nobody elses business.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>


</DD>

<DT><b><a name="showq_service_name">showq_service_name</a>
(default: showq)</b></DT><DD>

<p>
The name of the <a href="showq.8.html">showq(8)</a> service. This service produces mail queue
status reports.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>


</DD>

<DT><b><a name="smtp_always_send_ehlo">smtp_always_send_ehlo</a>
(default: yes)</b></DT><DD>

<p>
Always send EHLO at the start of an SMTP session.
</p>

<p>
With "<a href="postconf.5.html#smtp_always_send_ehlo">smtp_always_send_ehlo</a> = no", Postfix sends EHLO only when
the word "ESMTP" appears in the server greeting banner (example:
220 spike.porcupine.org ESMTP Postfix).
</p>


</DD>

<DT><b><a name="smtp_bind_address">smtp_bind_address</a>
(default: empty)</b></DT><DD>

<p>
An optional numerical network address that the Postfix SMTP client
should bind to when making an IPv4 connection.
</p>

<p>
This can be specified in the <a href="postconf.5.html">main.cf</a> file for all SMTP clients, or
it can be specified in the <a href="master.5.html">master.cf</a> file for a specific client,
for example:
</p>

<blockquote>
<pre>
/etc/postfix/<a href="master.5.html">master.cf</a>:
    smtp ... smtp -o <a href="postconf.5.html#smtp_bind_address">smtp_bind_address</a>=11.22.33.44
</pre>
</blockquote>

<p> Note 1: when <a href="postconf.5.html#inet_interfaces">inet_interfaces</a> specifies no more than one IPv4
address, and that address is a non-loopback address, it is
automatically used as the <a href="postconf.5.html#smtp_bind_address">smtp_bind_address</a>.  This supports virtual
IP hosting, but can be a problem on multi-homed firewalls. See the
<a href="postconf.5.html#inet_interfaces">inet_interfaces</a> documentation for more detail. </p>

<p> Note 2: address information may be enclosed inside <tt>[]</tt>,
but this form is not required here. </p>


</DD>

<DT><b><a name="smtp_bind_address6">smtp_bind_address6</a>
(default: empty)</b></DT><DD>

<p>
An optional numerical network address that the Postfix SMTP client
should bind to when making an IPv6 connection.
</p>

<p> This feature is available in Postfix 2.2 and later. </p>

<p>
This can be specified in the <a href="postconf.5.html">main.cf</a> file for all SMTP clients, or
it can be specified in the <a href="master.5.html">master.cf</a> file for a specific client,
for example:
</p>

<blockquote>
<pre>
/etc/postfix/<a href="master.5.html">master.cf</a>:
    smtp ... smtp -o <a href="postconf.5.html#smtp_bind_address6">smtp_bind_address6</a>=1:2:3:4:5:6:7:8
</pre>
</blockquote>

<p> Note 1: when <a href="postconf.5.html#inet_interfaces">inet_interfaces</a> specifies no more than one IPv6
address, and that address is a non-loopback address, it is
automatically used as the <a href="postconf.5.html#smtp_bind_address6">smtp_bind_address6</a>.  This supports virtual
IP hosting, but can be a problem on multi-homed firewalls. See the
<a href="postconf.5.html#inet_interfaces">inet_interfaces</a> documentation for more detail. </p>

<p> Note 2: address information may be enclosed inside <tt>[]</tt>,
but this form is not recommended here. </p>


</DD>

<DT><b><a name="smtp_body_checks">smtp_body_checks</a>
(default: empty)</b></DT><DD>

<p> Restricted <a href="header_checks.5.html">body_checks(5)</a> tables for the Postfix SMTP client.
These tables are searched while mail is being delivered.  Actions
that change the delivery time or destination are not available.
</p>

<p> This feature is available in Postfix 2.5 and later. </p>


</DD>

<DT><b><a name="smtp_cname_overrides_servername">smtp_cname_overrides_servername</a>
(default: version dependent)</b></DT><DD>

<p> Allow DNS CNAME records to override the servername that the
Postfix SMTP client uses for logging, SASL password lookup, TLS
policy decisions, or TLS certificate verification. The value "no"
hardens Postfix <a href="postconf.5.html#smtp_tls_per_site">smtp_tls_per_site</a> hostname-based policies against
false hostname information in DNS CNAME records, and makes SASL
password file lookups more predictable. This is the default setting
as of Postfix 2.3. </p>

<p> This feature is available in Postfix 2.2.9 and later. </p>


</DD>

<DT><b><a name="smtp_connect_timeout">smtp_connect_timeout</a>
(default: 30s)</b></DT><DD>

<p>
The SMTP client time limit for completing a TCP connection, or
zero (use the operating system built-in time limit).
</p>

<p>
When no connection can be made within the deadline, the Postfix
SMTP client
tries the next address on the mail exchanger list. Specify 0 to
disable the time limit (i.e. use whatever timeout is implemented by
the operating system).
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>


</DD>

<DT><b><a name="smtp_connection_cache_destinations">smtp_connection_cache_destinations</a>
(default: empty)</b></DT><DD>

<p> Permanently enable SMTP connection caching for the specified
destinations.  With SMTP connection caching, a connection is not
closed immediately after completion of a mail transaction.  Instead,
the connection is kept open for up to $<a href="postconf.5.html#smtp_connection_cache_time_limit">smtp_connection_cache_time_limit</a>
seconds.  This allows connections to be reused for other deliveries,
and can improve mail delivery performance. </p>

<p> Specify a comma or white space separated list of destinations
or pseudo-destinations: </p>

<ul>

<li> if mail is sent without a <a href="postconf.5.html#relayhost">relay host</a>: a domain name (the
right-hand side of an email address, without the [] around a numeric
IP address),

<li> if mail is sent via a <a href="postconf.5.html#relayhost">relay host</a>: a <a href="postconf.5.html#relayhost">relay host</a> name (without
[] or non-default TCP port), as specified in <a href="postconf.5.html">main.cf</a> or in the
transport map,

<li> if mail is sent via a UNIX-domain socket: a pathname (without
the unix: prefix),

<li> a /file/name with domain names and/or <a href="postconf.5.html#relayhost">relay host</a> names as
defined above,

<li> a "<a href="DATABASE_README.html">type:table</a>" with domain names and/or <a href="postconf.5.html#relayhost">relay host</a> names on
the left-hand side.  The right-hand side result from "<a href="DATABASE_README.html">type:table</a>"
lookups is ignored.

</ul>

<p> This feature is available in Postfix 2.2 and later. </p>


</DD>

<DT><b><a name="smtp_connection_cache_on_demand">smtp_connection_cache_on_demand</a>
(default: yes)</b></DT><DD>

<p> Temporarily enable SMTP connection caching while a destination
has a high volume of mail in the <a href="QSHAPE_README.html#active_queue">active queue</a>.  With SMTP connection
caching, a connection is not closed immediately after completion
of a mail transaction.  Instead, the connection is kept open for
up to $<a href="postconf.5.html#smtp_connection_cache_time_limit">smtp_connection_cache_time_limit</a> seconds.  This allows
connections to be reused for other deliveries, and can improve mail
delivery performance. </p>

<p> This feature is available in Postfix 2.2 and later. </p>


</DD>

<DT><b><a name="smtp_connection_cache_reuse_limit">smtp_connection_cache_reuse_limit</a>
(default: 10)</b></DT><DD>

<p> When SMTP connection caching is enabled, the number of times that
an SMTP session may be reused before it is closed.
</p>

<p> This feature is available in Postfix 2.2. In Postfix 2.3 it is
replaced by $<a href="postconf.5.html#smtp_connection_reuse_time_limit">smtp_connection_reuse_time_limit</a>.</p>


</DD>

<DT><b><a name="smtp_connection_cache_time_limit">smtp_connection_cache_time_limit</a>
(default: 2s)</b></DT><DD>

<p> When SMTP connection caching is enabled, the amount of time that
an unused SMTP client socket is kept open before it is closed.  Do
not specify larger values without permission from the remote sites.
</p>

<p> This feature is available in Postfix 2.2 and later. </p>


</DD>

<DT><b><a name="smtp_connection_reuse_time_limit">smtp_connection_reuse_time_limit</a>
(default: 300s)</b></DT><DD>

<p> The amount of time during which Postfix will use an SMTP
connection repeatedly.  The timer starts when the connection is
initiated (i.e. it includes the connect, greeting and helo latency,
in addition to the latencies of subsequent mail delivery transactions).
</p>

<p> This feature addresses a performance stability problem with
remote SMTP servers. This problem is not specific to Postfix: it
can happen when any MTA sends large amounts of SMTP email to a site
that has multiple MX hosts. </p>

<p> The problem starts when one of a set of MX hosts becomes slower
than the rest.  Even though SMTP clients connect to fast and slow
MX hosts with equal probability, the slow MX host ends up with more
simultaneous inbound connections than the faster MX hosts, because
the slow MX host needs more time to serve each client request. </p>

<p> The slow MX host becomes a connection attractor.  If one MX
host becomes N times slower than the rest, it dominates mail delivery
latency unless there are more than N fast MX hosts to counter the
effect. And if the number of MX hosts is smaller than N, the mail
delivery latency becomes effectively that of the slowest MX host
divided by the total number of MX hosts. </p>

<p> The solution uses connection caching in a way that differs from
Postfix version 2.2.  By limiting the amount of time during which a connection
can be used repeatedly (instead of limiting the number of deliveries
over that connection), Postfix not only restores fairness in the
distribution of simultaneous connections across a set of MX hosts,
it also favors deliveries over connections that perform well, which
is exactly what we want.  </p>

<p> The default reuse time limit, 300s, is comparable to the various
smtp transaction timeouts which are fair estimates of maximum excess
latency for a slow delivery.  Note that hosts may accept thousands
of messages over a single connection within the default connection
reuse time limit. This number is much larger than the default Postfix
version 2.2 limit of 10 messages per cached connection. It may prove necessary
to lower the limit to avoid interoperability issues with MTAs that
exhibit bugs when many messages are delivered via a single connection.
A lower reuse time limit risks losing the benefit of connection
reuse when the average connection and mail delivery latency exceeds
the reuse time limit.  </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="smtp_data_done_timeout">smtp_data_done_timeout</a>
(default: 600s)</b></DT><DD>

<p>
The SMTP client time limit for sending the SMTP ".", and for receiving
the server response.
</p>

<p>
When no response is received within the deadline, a warning is
logged that the mail may be delivered multiple times.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>


</DD>

<DT><b><a name="smtp_data_init_timeout">smtp_data_init_timeout</a>
(default: 120s)</b></DT><DD>

<p>
The SMTP client time limit for sending the SMTP DATA command, and for
receiving the server response.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>


</DD>

<DT><b><a name="smtp_data_xfer_timeout">smtp_data_xfer_timeout</a>
(default: 180s)</b></DT><DD>

<p>
The SMTP client time limit for sending the SMTP message content.
When the connection makes no progress for more than $<a href="postconf.5.html#smtp_data_xfer_timeout">smtp_data_xfer_timeout</a>
seconds the Postfix SMTP client terminates the transfer.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>


</DD>

<DT><b><a name="smtp_defer_if_no_mx_address_found">smtp_defer_if_no_mx_address_found</a>
(default: no)</b></DT><DD>

<p>
Defer mail delivery when no MX record resolves to an IP address.
</p>

<p>
The default (no) is to return the mail as undeliverable. With older
Postfix versions the default was to keep trying to deliver the mail
until someone fixed the MX record or until the mail was too old.
</p>

<p>
Note: Postfix always ignores MX records with equal or worse preference
than the local MTA itself.
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>


</DD>

<DT><b><a name="smtp_destination_concurrency_limit">smtp_destination_concurrency_limit</a>
(default: $<a href="postconf.5.html#default_destination_concurrency_limit">default_destination_concurrency_limit</a>)</b></DT><DD>

<p> The maximal number of parallel deliveries to the same destination
via the smtp message delivery transport. This limit is enforced by
the queue manager. The message delivery transport name is the first
field in the entry in the <a href="master.5.html">master.cf</a> file.  </p>


</DD>

<DT><b><a name="smtp_destination_recipient_limit">smtp_destination_recipient_limit</a>
(default: $<a href="postconf.5.html#default_destination_recipient_limit">default_destination_recipient_limit</a>)</b></DT><DD>

<p> The maximal number of recipients per delivery via the smtp
message delivery transport. This limit is enforced by the queue
manager. The message delivery transport name is the first field in
the entry in the <a href="master.5.html">master.cf</a> file.  </p>

<p> Setting this parameter to a value of 1 changes the meaning of
<a href="postconf.5.html#smtp_destination_concurrency_limit">smtp_destination_concurrency_limit</a> from concurrency per domain
into concurrency per recipient.  </p>


</DD>

<DT><b><a name="smtp_discard_ehlo_keyword_address_maps">smtp_discard_ehlo_keyword_address_maps</a>
(default: empty)</b></DT><DD>

<p> Lookup tables, indexed by the remote SMTP server address, with
case insensitive lists of EHLO keywords (pipelining, starttls, auth,
etc.) that the Postfix SMTP client will ignore in the EHLO response from a
remote SMTP server. See <a href="postconf.5.html#smtp_discard_ehlo_keywords">smtp_discard_ehlo_keywords</a> for details. The
table is not indexed by hostname for consistency with
<a href="postconf.5.html#smtpd_discard_ehlo_keyword_address_maps">smtpd_discard_ehlo_keyword_address_maps</a>. </p>

<p> This feature is available in Postfix 2.2 and later. </p>


</DD>

<DT><b><a name="smtp_discard_ehlo_keywords">smtp_discard_ehlo_keywords</a>
(default: empty)</b></DT><DD>

<p> A case insensitive list of EHLO keywords (pipelining, starttls,
auth, etc.) that the Postfix SMTP client will ignore in the EHLO
response from a remote SMTP server. </p>

<p> This feature is available in Postfix 2.2 and later. </p>

<p> Notes: </p>

<ul>

<li> <p> Specify the <b>silent-discard</b> pseudo keyword to prevent
this action from being logged. </p>

<li> <p> Use the <a href="postconf.5.html#smtp_discard_ehlo_keyword_address_maps">smtp_discard_ehlo_keyword_address_maps</a> feature to
discard EHLO keywords selectively. </p>

</ul>


</DD>

<DT><b><a name="smtp_enforce_tls">smtp_enforce_tls</a>
(default: no)</b></DT><DD>

<p> Enforcement mode: require that remote SMTP servers use TLS
encryption, and never send mail in the clear.  This also requires
that the remote SMTP server hostname matches the information in
the remote server certificate, and that the remote SMTP server
certificate was issued by a CA that is trusted by the Postfix SMTP
client. If the certificate doesn't verify or the hostname doesn't
match, delivery is deferred and mail stays in the queue.  </p>

<p> The server hostname is matched against all names provided as
dNSNames in the SubjectAlternativeName.  If no dNSNames are specified,
the CommonName is checked.  The behavior may be changed with the
<a href="postconf.5.html#smtp_tls_enforce_peername">smtp_tls_enforce_peername</a> option.  </p>

<p> This option is useful only if you are definitely sure that you
will only connect to servers that support <a href="http://tools.ietf.org/html/rfc2487">RFC 2487</a> _and_ that
provide valid server certificates.  Typical use is for clients that
send all their email to a dedicated mailhub.  </p>

<p> This feature is available in Postfix 2.2 and later. With
Postfix 2.3 and later use <a href="postconf.5.html#smtp_tls_security_level">smtp_tls_security_level</a> instead. </p>


</DD>

<DT><b><a name="smtp_fallback_relay">smtp_fallback_relay</a>
(default: $<a href="postconf.5.html#fallback_relay">fallback_relay</a>)</b></DT><DD>

<p>
Optional list of relay hosts for SMTP destinations that can't be
found or that are unreachable. With Postfix 2.2 and earlier this
parameter is called <a href="postconf.5.html#fallback_relay">fallback_relay</a>.  </p>

<p>
By default, mail is returned to the sender when a destination is
not found, and delivery is deferred when a destination is unreachable.
</p>

<p> The fallback relays must be SMTP destinations. Specify a domain,
host, host:port, [host]:port, [address] or [address]:port; the form
[host] turns off MX lookups.  If you specify multiple SMTP
destinations, Postfix will try them in the specified order.  </p>

<p> To prevent mailer loops between MX hosts and fall-back hosts,
Postfix version 2.2 and later will not use the fallback relays for
destinations that it is MX host for (and DSN lookup is turned on).
</p>


</DD>

<DT><b><a name="smtp_generic_maps">smtp_generic_maps</a>
(default: empty)</b></DT><DD>

<p> Optional lookup tables that perform address rewriting in the
SMTP client, typically to transform a locally valid address into
a globally valid address when sending mail across the Internet.
This is needed when the local machine does not have its own Internet
domain name, but uses something like <i>localdomain.local</i>
instead.  </p>

<p> The table format and lookups are documented in <a href="generic.5.html">generic(5)</a>;
examples are shown in the <a href="ADDRESS_REWRITING_README.html">ADDRESS_REWRITING_README</a> and
<a href="STANDARD_CONFIGURATION_README.html">STANDARD_CONFIGURATION_README</a> documents. </p>

<p> This feature is available in Postfix 2.2 and later.  </p>


</DD>

<DT><b><a name="smtp_header_checks">smtp_header_checks</a>
(default: empty)</b></DT><DD>

<p> Restricted <a href="header_checks.5.html">header_checks(5)</a> tables for the Postfix SMTP client.
These tables are searched while mail is being delivered.  Actions
that change the delivery time or destination are not available.
</p>

<p> This feature is available in Postfix 2.5 and later. </p>


</DD>

<DT><b><a name="smtp_helo_name">smtp_helo_name</a>
(default: $<a href="postconf.5.html#myhostname">myhostname</a>)</b></DT><DD>

<p>
The hostname to send in the SMTP EHLO or HELO command.
</p>

<p>
The default value is the machine hostname.  Specify a hostname or
[ip.add.re.ss].
</p>

<p>
This information can be specified in the <a href="postconf.5.html">main.cf</a> file for all SMTP
clients, or it can be specified in the <a href="master.5.html">master.cf</a> file for a specific
client, for example:
</p>

<blockquote>
<pre>
/etc/postfix/<a href="master.5.html">master.cf</a>:
    mysmtp ... smtp -o <a href="postconf.5.html#smtp_helo_name">smtp_helo_name</a>=foo.bar.com
</pre>
</blockquote>

<p>
This feature is available in Postfix 2.0 and later.
</p>


</DD>

<DT><b><a name="smtp_helo_timeout">smtp_helo_timeout</a>
(default: 300s)</b></DT><DD>

<p>
The SMTP client time limit for sending the HELO or EHLO command,
and for receiving the initial server response.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>


</DD>

<DT><b><a name="smtp_host_lookup">smtp_host_lookup</a>
(default: dns)</b></DT><DD>

<p>
What mechanisms when the Postfix SMTP client uses to look up a host's IP
address.  This parameter is ignored when DNS lookups are disabled.
</p>

<p>
Specify one of the following:
</p>

<dl>

<dt><b>dns</b></dt>

<dd>Hosts can be found in the DNS (preferred).  </dd>

<dt><b>native</b></dt>

<dd>Use the native naming service only (nsswitch.conf, or equivalent
mechanism).  </dd>

<dt><b>dns, native</b></dt>

<dd>Use the native service for hosts not found in the DNS.  </dd>

</dl>

<p>
This feature is available in Postfix 2.1 and later.
</p>


</DD>

<DT><b><a name="smtp_line_length_limit">smtp_line_length_limit</a>
(default: 990)</b></DT><DD>

<p>
The maximal length of message header and body lines that Postfix
will send via SMTP.  Longer lines are broken by inserting
"&lt;CR&gt;&lt;LF&gt;&lt;SPACE&gt;". This minimizes the damage to
MIME formatted mail.
</p>

<p>
By default, the line length is limited to 990 characters, because
some server implementations cannot receive mail with long lines.
</p>


</DD>

<DT><b><a name="smtp_mail_timeout">smtp_mail_timeout</a>
(default: 300s)</b></DT><DD>

<p>
The SMTP client time limit for sending the MAIL FROM command, and
for receiving the server response.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>


</DD>

<DT><b><a name="smtp_mime_header_checks">smtp_mime_header_checks</a>
(default: empty)</b></DT><DD>

<p> Restricted mime_<a href="header_checks.5.html">header_checks(5)</a> tables for the Postfix SMTP
client. These tables are searched while mail is being delivered.
Actions that change the delivery time or destination are not
available.  </p>

<p> This feature is available in Postfix 2.5 and later. </p>


</DD>

<DT><b><a name="smtp_mx_address_limit">smtp_mx_address_limit</a>
(default: 5)</b></DT><DD>

<p>
The maximal number of MX (mail exchanger) IP addresses that can
result from mail exchanger lookups, or zero (no limit). Prior to
Postfix version 2.3, this limit was disabled by default.
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>


</DD>

<DT><b><a name="smtp_mx_session_limit">smtp_mx_session_limit</a>
(default: 2)</b></DT><DD>

<p> The maximal number of SMTP sessions per delivery request before
giving up or delivering to a fall-back <a href="postconf.5.html#relayhost">relay host</a>, or zero (no
limit). This restriction ignores sessions that fail to complete the
SMTP initial handshake (Postfix version 2.2 and earlier) or that fail to
complete the EHLO and TLS handshake (Postfix version 2.3 and later).  </p>

<p> This feature is available in Postfix 2.1 and later.  </p>


</DD>

<DT><b><a name="smtp_nested_header_checks">smtp_nested_header_checks</a>
(default: empty)</b></DT><DD>

<p> Restricted nested_<a href="header_checks.5.html">header_checks(5)</a> tables for the Postfix SMTP
client. These tables are searched while mail is being delivered.
Actions that change the delivery time or destination are not
available.  </p>

<p> This feature is available in Postfix 2.5 and later. </p>


</DD>

<DT><b><a name="smtp_never_send_ehlo">smtp_never_send_ehlo</a>
(default: no)</b></DT><DD>

<p> Never send EHLO at the start of an SMTP session. See also the
<a href="postconf.5.html#smtp_always_send_ehlo">smtp_always_send_ehlo</a> parameter.  </p>


</DD>

<DT><b><a name="smtp_pix_workaround_delay_time">smtp_pix_workaround_delay_time</a>
(default: 10s)</b></DT><DD>

<p>
How long the Postfix SMTP client pauses before sending
".&lt;CR&gt;&lt;LF&gt;" in order to work around the PIX firewall
"&lt;CR&gt;&lt;LF&gt;.&lt;CR&gt;&lt;LF&gt;" bug.
</p>

<p>
Choosing a too short time makes this workaround ineffective when
sending large messages over slow network connections.
</p>


</DD>

<DT><b><a name="smtp_pix_workaround_maps">smtp_pix_workaround_maps</a>
(default: empty)</b></DT><DD>

<p> Lookup tables, indexed by the remote SMTP server address, with
per-destination workarounds for CISCO PIX firewall bugs.  The table
is not indexed by hostname for consistency with
<a href="postconf.5.html#smtp_discard_ehlo_keyword_address_maps">smtp_discard_ehlo_keyword_address_maps</a>. </p>

<p> This feature is available in Postfix 2.4 and later. </p>


</DD>

<DT><b><a name="smtp_pix_workaround_threshold_time">smtp_pix_workaround_threshold_time</a>
(default: 500s)</b></DT><DD>

<p> How long a message must be queued before the Postfix SMTP client
turns on the PIX firewall "&lt;CR&gt;&lt;LF&gt;.&lt;CR&gt;&lt;LF&gt;"
bug workaround for delivery through firewalls with "smtp fixup"
mode turned on.  </p>

<p>
By default, the workaround is turned off for mail that is queued
for less than 500 seconds. In other words, the workaround is normally
turned off for the first delivery attempt.
</p>

<p>
Specify 0 to enable the PIX firewall
"&lt;CR&gt;&lt;LF&gt;.&lt;CR&gt;&lt;LF&gt;" bug workaround upon the
first delivery attempt.
</p>


</DD>

<DT><b><a name="smtp_pix_workarounds">smtp_pix_workarounds</a>
(default: disable_esmtp, delay_dotcrlf)</b></DT><DD>

<p> A list that specifies zero or more workarounds for CISCO PIX
firewall bugs. These workarounds are implemented by the Postfix
SMTP client. Workaround names are separated by comma or space, and
are case insensitive.  This parameter setting can be overruled with
per-destination <a href="postconf.5.html#smtp_pix_workaround_maps">smtp_pix_workaround_maps</a> settings. </p>

<dl>

<dt><b>delay_dotcrlf</b><dd> Insert a delay before sending
".&lt;CR&gt;&lt;LF&gt;" after the end of the message content.  The
delay is subject to the <a href="postconf.5.html#smtp_pix_workaround_delay_time">smtp_pix_workaround_delay_time</a> and
<a href="postconf.5.html#smtp_pix_workaround_threshold_time">smtp_pix_workaround_threshold_time</a> parameter settings. </dd>

<dt><b>disable_esmtp</b><dd> Disable all extended SMTP commands:
send HELO instead of EHLO. </dd>

</dl>

<p> This feature is available in Postfix 2.4 and later. The default
settings are backwards compatible with earlier Postfix versions.
</p>


</DD>

<DT><b><a name="smtp_quit_timeout">smtp_quit_timeout</a>
(default: 300s)</b></DT><DD>

<p>
The SMTP client time limit for sending the QUIT command, and for
receiving the server response.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>


</DD>

<DT><b><a name="smtp_quote_rfc821_envelope">smtp_quote_rfc821_envelope</a>
(default: yes)</b></DT><DD>

<p>
Quote addresses in SMTP MAIL FROM and RCPT TO commands as required
by <a href="http://tools.ietf.org/html/rfc821">RFC 821</a>. This includes putting quotes around an address localpart
that ends in ".".
</p>

<p>
The default is to comply with <a href="http://tools.ietf.org/html/rfc821">RFC 821</a>. If you have to send mail to
a broken SMTP server, configure a special SMTP client in <a href="master.5.html">master.cf</a>:
</p>

<blockquote>
<pre>
/etc/postfix/<a href="master.5.html">master.cf</a>:
    broken-smtp . . . smtp -o <a href="postconf.5.html#smtp_quote_rfc821_envelope">smtp_quote_rfc821_envelope</a>=no
</pre>
</blockquote>

<p>
and route mail for the destination in question to the "broken-smtp"
message delivery with a <a href="transport.5.html">transport(5)</a> table.
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>


</DD>

<DT><b><a name="smtp_randomize_addresses">smtp_randomize_addresses</a>
(default: yes)</b></DT><DD>

<p>
Randomize the order of equal-preference MX host addresses.  This
is a performance feature of the Postfix SMTP client.
</p>


</DD>

<DT><b><a name="smtp_rcpt_timeout">smtp_rcpt_timeout</a>
(default: 300s)</b></DT><DD>

<p>
The SMTP client time limit for sending the SMTP RCPT TO command, and
for receiving the server response.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>


</DD>

<DT><b><a name="smtp_rset_timeout">smtp_rset_timeout</a>
(default: 20s)</b></DT><DD>

<p> The SMTP client time limit for sending the RSET command, and
for receiving the server response. The SMTP client sends RSET in
order to finish a recipient address probe, or to verify that a
cached session is still usable.  </p>

<p> This feature is available in Postfix 2.1 and later.  </p>


</DD>

<DT><b><a name="smtp_sasl_auth_cache_name">smtp_sasl_auth_cache_name</a>
(default: empty)</b></DT><DD>

<p> An optional table to prevent repeated SASL authentication
failures with the same remote SMTP server hostname, username and
password. Each table (key, value) pair contains a server name, a
username and password, and the full server response. This information
is stored when a remote SMTP server rejects an authentication attempt
with a 535 reply code.  As long as the <a href="postconf.5.html#smtp_sasl_password_maps">smtp_sasl_password_maps</a>
information does no change, and as long as the <a href="postconf.5.html#smtp_sasl_auth_cache_name">smtp_sasl_auth_cache_name</a>
information does not expire (see <a href="postconf.5.html#smtp_sasl_auth_cache_time">smtp_sasl_auth_cache_time</a>) the
Postfix SMTP client avoids SASL authentication attempts with the
same server, username and password, and instead bounces or defers
mail as controlled with the <a href="postconf.5.html#smtp_sasl_auth_soft_bounce">smtp_sasl_auth_soft_bounce</a> configuration
parameter.  </p>

<p> Use a per-destination delivery concurrency of 1 (for example,
"<a href="postconf.5.html#smtp_destination_concurrency_limit">smtp_destination_concurrency_limit</a> = 1",
"<a href="postconf.5.html#relay_destination_concurrency_limit">relay_destination_concurrency_limit</a> = 1", etc.), otherwise multiple
delivery agents may experience a login failure at the same time.
</p>

<p> The table must be accessed via the proxywrite service, i.e. the
map name must start with "<a href="proxymap.8.html">proxy</a>:". The table should be stored under
the directory specified with the <a href="postconf.5.html#data_directory">data_directory</a> parameter. </p>

<p> This feature uses cryptographic hashing to protect plain-text
passwords, and requires that Postfix is compiled with TLS support.
</p>

<p> Example: </p>

<pre>
<a href="postconf.5.html#smtp_sasl_auth_cache_name">smtp_sasl_auth_cache_name</a> = <a href="proxymap.8.html">proxy</a>:btree:/var/lib/postfix/sasl_auth_cache
</pre>

<p> This feature is available in Postfix 2.5 and later. </p>


</DD>

<DT><b><a name="smtp_sasl_auth_cache_time">smtp_sasl_auth_cache_time</a>
(default: 90d)</b></DT><DD>

<p> The maximal age of an <a href="postconf.5.html#smtp_sasl_auth_cache_name">smtp_sasl_auth_cache_name</a> entry before it
is removed. </p>

<p> This feature is available in Postfix 2.5 and later. </p>


</DD>

<DT><b><a name="smtp_sasl_auth_enable">smtp_sasl_auth_enable</a>
(default: no)</b></DT><DD>

<p>
Enable SASL authentication in the Postfix SMTP client.  By default,
the Postfix SMTP client uses no authentication.
</p>

<p>
Example:
</p>

<pre>
<a href="postconf.5.html#smtp_sasl_auth_enable">smtp_sasl_auth_enable</a> = yes
</pre>


</DD>

<DT><b><a name="smtp_sasl_auth_soft_bounce">smtp_sasl_auth_soft_bounce</a>
(default: yes)</b></DT><DD>

<p> When a remote SMTP server rejects a SASL authentication request
with a 535 reply code, defer mail delivery instead of returning
mail as undeliverable. The latter behavior was hard-coded prior to
Postfix version 2.5. </p>

<p> Note: the setting "yes" overrides the global <a href="postconf.5.html#soft_bounce">soft_bounce</a>
parameter, but the setting "no" does not. </p>

<p> Example: </p>

<pre>
# Default as of Postfix 2.5
<a href="postconf.5.html#smtp_sasl_auth_soft_bounce">smtp_sasl_auth_soft_bounce</a> = yes
# The old hard-coded default
<a href="postconf.5.html#smtp_sasl_auth_soft_bounce">smtp_sasl_auth_soft_bounce</a> = no
</pre>

<p> This feature is available in Postfix 2.5 and later. </p>


</DD>

<DT><b><a name="smtp_sasl_mechanism_filter">smtp_sasl_mechanism_filter</a>
(default: empty)</b></DT><DD>

<p>
If non-empty, a Postfix SMTP client filter for the remote SMTP
server's list of offered SASL mechanisms.  Different client and
server implementations may support different mechanism lists. By
default, the Postfix SMTP client will use the intersection of the
two. <a href="postconf.5.html#smtp_sasl_mechanism_filter">smtp_sasl_mechanism_filter</a> further restricts what server
mechanisms the client will take into consideration.  </p>

<p> Specify mechanism names, "/file/name" patterns or "<a href="DATABASE_README.html">type:table</a>"
lookup tables. The right-hand side result from "<a href="DATABASE_README.html">type:table</a>" lookups
is ignored. Specify "!pattern" to exclude a mechanism name from the
list. The form "!/file/name" is supported only in Postfix version
2.4 and later. </p>

<p> This feature is available in Postfix 2.2 and later. </p>

<p>
Examples:
</p>

<pre>
<a href="postconf.5.html#smtp_sasl_mechanism_filter">smtp_sasl_mechanism_filter</a> = plain, login
<a href="postconf.5.html#smtp_sasl_mechanism_filter">smtp_sasl_mechanism_filter</a> = /etc/postfix/smtp_mechs
<a href="postconf.5.html#smtp_sasl_mechanism_filter">smtp_sasl_mechanism_filter</a> = !gssapi, !login, static:rest
</pre>


</DD>

<DT><b><a name="smtp_sasl_password_maps">smtp_sasl_password_maps</a>
(default: empty)</b></DT><DD>

<p>
Optional SMTP client lookup tables with one username:password entry
per remote hostname or domain, or sender address when sender-dependent
authentication is enabled.  If no username:password entry is found,
then the Postfix SMTP client will not
attempt to authenticate to the remote host.
</p>

<p>
The Postfix SMTP client opens the lookup table before going to
chroot jail, so you can leave the password file in /etc/postfix.
</p>


</DD>

<DT><b><a name="smtp_sasl_path">smtp_sasl_path</a>
(default: empty)</b></DT><DD>

<p> Implementation-specific information that the Postfix SMTP client
passes through to
the SASL plug-in implementation that is selected with
<b><a href="postconf.5.html#smtp_sasl_type">smtp_sasl_type</a></b>.  Typically this specifies the name of a
configuration file or rendezvous point. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="smtp_sasl_security_options">smtp_sasl_security_options</a>
(default: noplaintext, noanonymous)</b></DT><DD>

<p> Postfix SMTP client SASL security options; as of Postfix 2.3
the list of available
features depends on the SASL client implementation that is selected
with <b><a href="postconf.5.html#smtp_sasl_type">smtp_sasl_type</a></b>.  </p>

<p> The following security features are defined for the <b>cyrus</b>
client SASL implementation: </p>

<p>
Specify zero or more of the following:
</p>

<dl>

<dt><b>noplaintext</b></dt>

<dd>Disallow methods that use plaintext passwords. </dd>

<dt><b>noactive</b></dt>

<dd>Disallow methods subject to active (non-dictionary) attack.
</dd>

<dt><b>nodictionary</b></dt>

<dd>Disallow methods subject to passive (dictionary) attack. </dd>

<dt><b>noanonymous</b></dt>

<dd>Disallow methods that allow anonymous authentication. </dd>

<dt><b>mutual_auth</b></dt>

<dd>Only allow methods that provide mutual authentication (not
available with SASL version 1). </dd>

</dl>

<p>
Example:
</p>

<pre>
<a href="postconf.5.html#smtp_sasl_security_options">smtp_sasl_security_options</a> = noplaintext
</pre>


</DD>

<DT><b><a name="smtp_sasl_tls_security_options">smtp_sasl_tls_security_options</a>
(default: $<a href="postconf.5.html#smtp_sasl_security_options">smtp_sasl_security_options</a>)</b></DT><DD>

<p> The SASL authentication security options that the Postfix SMTP
client uses for TLS encrypted SMTP sessions. </p>

<p> This feature is available in Postfix 2.2 and later.  </p>


</DD>

<DT><b><a name="smtp_sasl_tls_verified_security_options">smtp_sasl_tls_verified_security_options</a>
(default: $<a href="postconf.5.html#smtp_sasl_tls_security_options">smtp_sasl_tls_security_options</a>)</b></DT><DD>

<p> The SASL authentication security options that the Postfix SMTP
client uses for TLS encrypted SMTP sessions with a verified server
certificate. This feature is under construction as of Postfix version
2.3. </p>


</DD>

<DT><b><a name="smtp_sasl_type">smtp_sasl_type</a>
(default: cyrus)</b></DT><DD>

<p> The SASL plug-in type that the Postfix SMTP client should use
for authentication.  The available types are listed with the
"<b>postconf -A</b>" command. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="smtp_send_xforward_command">smtp_send_xforward_command</a>
(default: no)</b></DT><DD>

<p>
Send the non-standard XFORWARD command when the Postfix SMTP server
EHLO response announces XFORWARD support.
</p>

<p>
This allows an "smtp" delivery agent, used for injecting mail into
a content filter, to forward the name, address, protocol and HELO
name of the original client to the content filter and downstream
queuing SMTP server. This can produce more useful logging than
localhost[127.0.0.1] etc.
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>


</DD>

<DT><b><a name="smtp_sender_dependent_authentication">smtp_sender_dependent_authentication</a>
(default: no)</b></DT><DD>

<p>
Enable sender-dependent authentication in the Postfix SMTP client; this is
available only with SASL authentication, and disables SMTP connection
caching to ensure that mail from different senders will use the
appropriate credentials.  </p>

<p>
This feature is available in Postfix 2.3 and later.
</p>


</DD>

<DT><b><a name="smtp_skip_4xx_greeting">smtp_skip_4xx_greeting</a>
(default: yes)</b></DT><DD>

<p>
Skip SMTP servers that greet with a 4XX status code (go away, try
again later).
</p>

<p>
By default, Postfix moves on the next mail exchanger. Specify
"<a href="postconf.5.html#smtp_skip_4xx_greeting">smtp_skip_4xx_greeting</a> = no" if Postfix should defer delivery
immediately.
</p>

<p> This feature is available in Postfix 2.0 and earlier.
Later Postfix versions always skip SMTP servers that greet with a
4XX status code. </p>


</DD>

<DT><b><a name="smtp_skip_5xx_greeting">smtp_skip_5xx_greeting</a>
(default: yes)</b></DT><DD>

<p>
Skip SMTP servers that greet with a 5XX status code (go away, do
not try again later).
</p>

<p> By default, the Postfix SMTP client moves on the next mail
exchanger. Specify "<a href="postconf.5.html#smtp_skip_5xx_greeting">smtp_skip_5xx_greeting</a> = no" if Postfix should
bounce the mail immediately. The default setting is incorrect, but
it is what a lot of people expect to happen.  </p>


</DD>

<DT><b><a name="smtp_skip_quit_response">smtp_skip_quit_response</a>
(default: yes)</b></DT><DD>

<p>
Do not wait for the response to the SMTP QUIT command.
</p>


</DD>

<DT><b><a name="smtp_starttls_timeout">smtp_starttls_timeout</a>
(default: 300s)</b></DT><DD>

<p> Time limit for Postfix SMTP client write and read operations
during TLS startup and shutdown handshake procedures. </p>

<p> This feature is available in Postfix 2.2 and later.  </p>


</DD>

<DT><b><a name="smtp_tls_CAfile">smtp_tls_CAfile</a>
(default: empty)</b></DT><DD>

<p> The file with the certificate of the certification authority
(CA) that issued the Postfix SMTP client certificate.  This is
needed only when the CA certificate is not already present in the
client certificate file.  </p>

<p> Example: </p>

<pre>
<a href="postconf.5.html#smtp_tls_CAfile">smtp_tls_CAfile</a> = /etc/postfix/CAcert.pem
</pre>

<p> This feature is available in Postfix 2.2 and later.  </p>


</DD>

<DT><b><a name="smtp_tls_CApath">smtp_tls_CApath</a>
(default: empty)</b></DT><DD>

<p> Directory with PEM format certificate authority certificates
that the Postfix SMTP client uses to verify a remote SMTP server
certificate.  Don't forget to create the necessary "hash" links
with, for example, "$OPENSSL_HOME/bin/c_rehash /etc/postfix/certs".
</p>

<p> To use this option in chroot mode, this directory (or a copy)
must be inside the chroot jail. </p>

<p> Example: </p>

<pre>
<a href="postconf.5.html#smtp_tls_CApath">smtp_tls_CApath</a> = /etc/postfix/certs
</pre>

<p> This feature is available in Postfix 2.2 and later.  </p>


</DD>

<DT><b><a name="smtp_tls_cert_file">smtp_tls_cert_file</a>
(default: empty)</b></DT><DD>

<p> File with the Postfix SMTP client RSA certificate in PEM format.
This file may also contain the Postfix SMTP client private RSA key,
and these may be the same as the Postfix SMTP server RSA certificate and key
file. </p>

<p> Do not configure client certificates unless you <b>must</b> present
client TLS certificates to one or more servers. Client certificates are
not usually needed, and can cause problems in configurations that work
well without them. The recommended setting is to let the defaults stand: </p>

<blockquote>
<pre>
<a href="postconf.5.html#smtp_tls_cert_file">smtp_tls_cert_file</a> =
<a href="postconf.5.html#smtp_tls_dcert_file">smtp_tls_dcert_file</a> =
<a href="postconf.5.html#smtp_tls_key_file">smtp_tls_key_file</a> =
<a href="postconf.5.html#smtp_tls_dkey_file">smtp_tls_dkey_file</a> =
</pre>
</blockquote>

<p> The best way to use the default settings is to comment out the above
parameters in <a href="postconf.5.html">main.cf</a> if present. </p>

<p> In order to verify certificates, the CA certificate (in case
of a certificate chain, all CA certificates) must be available.
You should add these certificates to the client certificate, the
client certificate first, then the issuing CA(s). </p>

<p> Example: the certificate for "client.dom.ain" was issued by
"intermediate CA" which itself has a certificate of "root CA".
Create the client.pem file with "cat client_cert.pem intermediate_CA.pem
root_CA.pem &gt; client.pem". </p>

<p> If you also want to verify remote SMTP server certificates issued by
these CAs, you can also add the CA certificates to the <a href="postconf.5.html#smtp_tls_CAfile">smtp_tls_CAfile</a>,
in which case it is not necessary to have them in the <a href="postconf.5.html#smtp_tls_cert_file">smtp_tls_cert_file</a>
or <a href="postconf.5.html#smtp_tls_dcert_file">smtp_tls_dcert_file</a>. </p>

<p> A certificate supplied here must be usable as an SSL client certificate
and hence pass the "openssl verify -purpose sslclient ..." test. </p>

<p> Example: </p>

<pre>
<a href="postconf.5.html#smtp_tls_cert_file">smtp_tls_cert_file</a> = /etc/postfix/client.pem
</pre>

<p> This feature is available in Postfix 2.2 and later.  </p>


</DD>

<DT><b><a name="smtp_tls_cipherlist">smtp_tls_cipherlist</a>
(default: empty)</b></DT><DD>

<p> Obsolete Postfix &lt; 2.3 control for the Postfix SMTP client TLS
cipher list. As this feature applies to all TLS security levels, it is easy
to create inter-operability problems by choosing a non-default cipher
list. Do not use a non-default TLS cipher list on hosts that deliver email
to the public Internet: you will be unable to send email to servers that
only support the ciphers you exclude. Using a restricted cipher list
may be more appropriate for an internal MTA, where one can exert some
control over the TLS software and settings of the peer servers. </p>

<p> <b>Note:</b> do not use "" quotes around the parameter value. </p>

<p> This feature is available in Postfix version 2.2. It is not used with
Postfix 2.3 and later; use <a href="postconf.5.html#smtp_tls_mandatory_ciphers">smtp_tls_mandatory_ciphers</a> instead. </p>


</DD>

<DT><b><a name="smtp_tls_dcert_file">smtp_tls_dcert_file</a>
(default: empty)</b></DT><DD>

<p> File with the Postfix SMTP client DSA certificate in PEM format.
This file may also contain the Postfix SMTP client private DSA key. </p>

<p> See the discussion under <a href="postconf.5.html#smtp_tls_cert_file">smtp_tls_cert_file</a> for more details.
</p>

<p> Example: </p>

<pre>
<a href="postconf.5.html#smtp_tls_dcert_file">smtp_tls_dcert_file</a> = /etc/postfix/client-dsa.pem
</pre>

<p> This feature is available in Postfix 2.2 and later.  </p>


</DD>

<DT><b><a name="smtp_tls_dkey_file">smtp_tls_dkey_file</a>
(default: $<a href="postconf.5.html#smtp_tls_dcert_file">smtp_tls_dcert_file</a>)</b></DT><DD>

<p> File with the Postfix SMTP client DSA private key in PEM format.
This file may be combined with the Postfix SMTP client DSA certificate
file specified with $<a href="postconf.5.html#smtp_tls_dcert_file">smtp_tls_dcert_file</a>. </p>

<p> The private key must be accessible without a pass-phrase, i.e. it
must not be encrypted, but file permissions should grant read/write
access only to the system superuser account ("root"). </p>

<p> This feature is available in Postfix 2.2 and later.  </p>


</DD>

<DT><b><a name="smtp_tls_enforce_peername">smtp_tls_enforce_peername</a>
(default: yes)</b></DT><DD>

<p> With mandatory TLS encryption, require that the remote SMTP
server hostname matches the information in the remote SMTP server
certificate.  As of <a href="http://tools.ietf.org/html/rfc2487">RFC 2487</a> the requirements for hostname checking
for MTA clients are not specified. </p>

<p> This option can be set to "no" to disable strict peer name
checking. This setting has no effect on sessions that are controlled
via the <a href="postconf.5.html#smtp_tls_per_site">smtp_tls_per_site</a> table.  </p>

<p> Disabling the hostname verification can make sense in closed
environment where special CAs are created.  If not used carefully,
this option opens the danger of a "man-in-the-middle" attack (the
CommonName of this attacker will be logged). </p>

<p> This feature is available in Postfix 2.2 and later. With
Postfix 2.3 and later use <a href="postconf.5.html#smtp_tls_security_level">smtp_tls_security_level</a> instead. </p>


</DD>

<DT><b><a name="smtp_tls_exclude_ciphers">smtp_tls_exclude_ciphers</a>
(default: empty)</b></DT><DD>

<p> List of ciphers or cipher types to exclude from the Postfix
SMTP client cipher
list at all TLS security levels. This is not an OpenSSL cipherlist, it is
a simple list separated by whitespace and/or commas. The elements are a
single cipher, or one or more "+" separated cipher properties, in which
case only ciphers matching <b>all</b> the properties are excluded. </p>

<p> Examples (some of these will cause problems): </p>

<blockquote>
<pre>
<a href="postconf.5.html#smtp_tls_exclude_ciphers">smtp_tls_exclude_ciphers</a> = aNULL
<a href="postconf.5.html#smtp_tls_exclude_ciphers">smtp_tls_exclude_ciphers</a> = MD5, DES
<a href="postconf.5.html#smtp_tls_exclude_ciphers">smtp_tls_exclude_ciphers</a> = DES+MD5
<a href="postconf.5.html#smtp_tls_exclude_ciphers">smtp_tls_exclude_ciphers</a> = AES256-SHA, DES-CBC3-MD5
<a href="postconf.5.html#smtp_tls_exclude_ciphers">smtp_tls_exclude_ciphers</a> = kEDH+aRSA
</pre>
</blockquote>

<p> The first setting, disables anonymous ciphers. The next setting
disables ciphers that use the MD5 digest algorithm or the (single) DES
encryption algorithm. The next setting disables ciphers that use MD5 and
DES together.  The next setting disables the two ciphers "AES256-SHA"
and "DES-CBC3-MD5". The last setting disables ciphers that use "EDH"
key exchange with RSA authentication. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="smtp_tls_fingerprint_cert_match">smtp_tls_fingerprint_cert_match</a>
(default: empty)</b></DT><DD>

<p> List of acceptable remote SMTP server certificate fingerprints
for the "fingerprint" TLS security level (<b><a href="postconf.5.html#smtp_tls_security_level">smtp_tls_security_level</a></b> =
fingerprint). At this security level, certificate authorities are
not used, and certificate expiration times are ignored. Instead,
server certificates are verified directly via their "fingerprint". The
fingerprint is a message digest of the server certificate. The digest
algorithm is selected via the <b><a href="postconf.5.html#smtp_tls_fingerprint_digest">smtp_tls_fingerprint_digest</a></b>
parameter. </p>

<p> When an <b><a href="postconf.5.html#smtp_tls_policy_maps">smtp_tls_policy_maps</a></b> table entry specifies the
"fingerprint" security level, any "match" attributes in that entry specify
the list of valid fingerprints for the corresponding destination. Multiple
fingerprints can be combined with a "|" delimiter in a single match
attribute, or multiple match attributes can be employed. </p>

<p> Example: Certificate fingerprint verification with internal mailhub.
Two matching fingerprints are listed. The <a href="postconf.5.html#relayhost">relayhost</a> may be multiple
physical hosts behind a load-balancer, each with its own private/public
key and self-signed certificate. Alternatively, a single <a href="postconf.5.html#relayhost">relayhost</a> may
be in the process of switching from one set of private/public keys to
another, and both keys are trusted just prior to the transition. </p>

<blockquote>
<pre>
<a href="postconf.5.html#relayhost">relayhost</a> = [mailhub.example.com]
<a href="postconf.5.html#smtp_tls_security_level">smtp_tls_security_level</a> = fingerprint
<a href="postconf.5.html#smtp_tls_fingerprint_digest">smtp_tls_fingerprint_digest</a> = md5
<a href="postconf.5.html#smtp_tls_fingerprint_cert_match">smtp_tls_fingerprint_cert_match</a> =
    3D:95:34:51:24:66:33:B9:D2:40:99:C0:C1:17:0B:D1
    EC:3B:2D:B0:5B:B1:FB:6D:20:A3:9D:72:F6:8D:12:35
</pre>
</blockquote>

<p> Example: Certificate fingerprint verification with selected destinations.
As in the example above, we show two matching fingerprints: </p>

<blockquote>
<pre>
/etc/postfix/<a href="postconf.5.html">main.cf</a>:
    <a href="postconf.5.html#smtp_tls_policy_maps">smtp_tls_policy_maps</a> = hash:/etc/postfix/tls_policy
    <a href="postconf.5.html#smtp_tls_fingerprint_digest">smtp_tls_fingerprint_digest</a> = md5
</pre>
</blockquote>

<blockquote>
<pre>
/etc/postfix/tls_policy:
    example.com	fingerprint
        match=3D:95:34:51:24:66:33:B9:D2:40:99:C0:C1:17:0B:D1
        match=EC:3B:2D:B0:5B:B1:FB:6D:20:A3:9D:72:F6:8D:12:35
</pre>
</blockquote>

<p> This feature is available in Postfix 2.5 and later. </p>


</DD>

<DT><b><a name="smtp_tls_fingerprint_digest">smtp_tls_fingerprint_digest</a>
(default: md5)</b></DT><DD>

<p> The message digest algorithm used to construct remote SMTP server
certificate fingerprints. At the "fingerprint" TLS security level
(<b><a href="postconf.5.html#smtp_tls_security_level">smtp_tls_security_level</a></b> = fingerprint), the server certificate is
verified by directly matching its <i>fingerprint</i>. The fingerprint
is the message digest of the server certificate using the selected
algorithm. With a digest algorithm resistant to "second pre-image"
attacks, it is not feasible to create a new public key and a matching
certificate that has the same fingerprint. </p>

<p> The default algorithm is <b>md5</b>; this is consistent with
the backwards compatible setting of the digest used to verify client
certificates in the SMTP server. </p>

<p> The best practice algorithm is now <b>sha1</b>. Recent advances in hash
function cryptanalysis have led to md5 being deprecated in favor of sha1.
However, as long as there are no known "second pre-image" attacks
against md5, its use in this context can still be considered safe.
</p>

<p> While additional digest algorithms are often available with OpenSSL's
libcrypto, only those used by libssl in SSL cipher suites are available to
Postfix. For now this means just md5 or sha1. </p>

<p> To find the fingerprint of a specific certificate file, with a
specific digest algorithm, run:
</p>

<blockquote>
<pre>
$ openssl x509 -noout -fingerprint -<i>digest</i> -in <i>certfile</i>.pem
</pre>
</blockquote>

<p> The text to the right of "=" sign is the desired fingerprint.
For example: </p>

<blockquote>
<pre>
$ openssl x509 -noout -fingerprint -sha1 -in cert.pem
SHA1 Fingerprint=D4:6A:AB:19:24:79:F8:32:BB:A6:CB:66:82:C0:8E:9B:EE:29:A8:1A
</pre>
</blockquote>

<p> This feature is available in Postfix 2.5 and later. </p>


</DD>

<DT><b><a name="smtp_tls_key_file">smtp_tls_key_file</a>
(default: $<a href="postconf.5.html#smtp_tls_cert_file">smtp_tls_cert_file</a>)</b></DT><DD>

<p> File with the Postfix SMTP client RSA private key in PEM format.
This file may be combined with the Postfix SMTP client RSA certificate
file specified with $<a href="postconf.5.html#smtp_tls_cert_file">smtp_tls_cert_file</a>. </p>

<p> The private key must be accessible without a pass-phrase, i.e. it
must not be encrypted, but file permissions should grant read/write
access only to the system superuser account ("root"). </p>

<p> Example: </p>

<pre>
<a href="postconf.5.html#smtp_tls_key_file">smtp_tls_key_file</a> = $<a href="postconf.5.html#smtp_tls_cert_file">smtp_tls_cert_file</a>
</pre>

<p> This feature is available in Postfix 2.2 and later.  </p>


</DD>

<DT><b><a name="smtp_tls_loglevel">smtp_tls_loglevel</a>
(default: 0)</b></DT><DD>

<p> Enable additional Postfix SMTP client logging of TLS activity.
Each logging level also includes the information that is logged at
a lower logging level.  </p>

<dl compact>

<dt> </dt> <dd> 0 Disable logging of TLS activity. </dd>

<dt> </dt> <dd> 1 Log TLS handshake and certificate information. </dd>

<dt> </dt> <dd> 2 Log levels during TLS negotiation. </dd>

<dt> </dt> <dd> 3 Log hexadecimal and ASCII dump of TLS negotiation
process.  </dd>

<dt> </dt> <dd> 4 Log hexadecimal and ASCII dump of complete
transmission after STARTTLS. </dd>

</dl>

<p> Use "<a href="postconf.5.html#smtp_tls_loglevel">smtp_tls_loglevel</a> = 3" only in case of problems. Use of
loglevel 4 is strongly discouraged. </p>

<p> This feature is available in Postfix 2.2 and later.  </p>


</DD>

<DT><b><a name="smtp_tls_mandatory_ciphers">smtp_tls_mandatory_ciphers</a>
(default: medium)</b></DT><DD>

<p> The minimum TLS cipher grade that the Postfix SMTP client will
use with
mandatory TLS encryption.  The default value "medium" is suitable
for most destinations with which you may want to enforce TLS, and
is beyond the reach of today's crypt-analytic methods. See
<a href="postconf.5.html#smtp_tls_policy_maps">smtp_tls_policy_maps</a> for information on how to configure ciphers
on a per-destination basis. </p>

<p> The following cipher grades are supported: </p>

<dl>
<dt><b>export</b></dt>
<dd> Enable the mainstream "EXPORT" grade or better OpenSSL
ciphers.  This is always used for opportunistic encryption. It is
not recommended for mandatory encryption unless you must enforce TLS
with "crippled" peers. The underlying cipherlist is specified via the
<a href="postconf.5.html#tls_export_cipherlist">tls_export_cipherlist</a> configuration parameter, which you are strongly
encouraged to not change. The default value of <a href="postconf.5.html#tls_export_cipherlist">tls_export_cipherlist</a>
includes anonymous ciphers, but these are automatically filtered out if
the client is configured to verify server certificates. If you must
exclude anonymous ciphers also at the "encrypt" security level, set
"<a href="postconf.5.html#smtp_tls_mandatory_exclude_ciphers">smtp_tls_mandatory_exclude_ciphers</a> = aNULL". </dd>

<dt><b>low</b></dt>
<dd> Enable the mainstream "LOW" grade or better OpenSSL ciphers.  This
setting is only appropriate for internal mail servers.  The underlying
cipherlist is specified via the <a href="postconf.5.html#tls_low_cipherlist">tls_low_cipherlist</a> configuration
parameter, which you are strongly encouraged to not change. The default
value of <a href="postconf.5.html#tls_low_cipherlist">tls_low_cipherlist</a> includes anonymous ciphers, but these are
automatically filtered out if the client is configured to verify server
certificates. If you must exclude anonymous ciphers also at the "encrypt"
security level, set "<a href="postconf.5.html#smtp_tls_mandatory_exclude_ciphers">smtp_tls_mandatory_exclude_ciphers</a> = aNULL". </dd>

<dt><b>medium</b></dt>
<dd> Enable the mainstream "MEDIUM" grade or better OpenSSL ciphers.
The underlying cipherlist is specified via the <a href="postconf.5.html#tls_medium_cipherlist">tls_medium_cipherlist</a>
configuration parameter, which you are strongly encouraged to not change.
The default value of <a href="postconf.5.html#tls_medium_cipherlist">tls_medium_cipherlist</a> includes anonymous ciphers,
but these are automatically filtered out if the client is configured to
verify server certificates. If you must exclude anonymous ciphers also
at the "encrypt" security level, set "<a href="postconf.5.html#smtp_tls_mandatory_exclude_ciphers">smtp_tls_mandatory_exclude_ciphers</a>
= aNULL". </dd>

<dt><b>high</b></dt>
<dd> Enable only the mainstream "HIGH" grade OpenSSL ciphers.  This
setting is appropriate when all mandatory TLS destinations support
some of "HIGH" grade ciphers, this is not uncommon. The underlying
cipherlist is specified via the <a href="postconf.5.html#tls_high_cipherlist">tls_high_cipherlist</a> configuration
parameter, which you are strongly encouraged to not change. The default
value of <a href="postconf.5.html#tls_high_cipherlist">tls_high_cipherlist</a> includes anonymous ciphers, but these are
automatically filtered out if the client is configured to verify server
certificates. If you must exclude anonymous ciphers also at the "encrypt"
security level, set "<a href="postconf.5.html#smtp_tls_mandatory_exclude_ciphers">smtp_tls_mandatory_exclude_ciphers</a> = aNULL". </dd>

<dt><b>null</b></dt>
<dd> Enable only the "NULL" OpenSSL ciphers, these provide authentication
without encryption.  This setting is only appropriate in the rare case
that all servers are prepared to use NULL ciphers (not normally enabled
in TLS servers). A plausible use-case is an LMTP server listening on a
UNIX-domain socket that is configured to support "NULL" ciphers. The
underlying cipherlist is specified via the <a href="postconf.5.html#tls_null_cipherlist">tls_null_cipherlist</a>
configuration parameter, which you are strongly encouraged to not
change. The default value of <a href="postconf.5.html#tls_null_cipherlist">tls_null_cipherlist</a> excludes anonymous
ciphers (OpenSSL 0.9.8 has NULL ciphers that offer data integrity without
encryption or authentication). </dd>

</dl>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="smtp_tls_mandatory_exclude_ciphers">smtp_tls_mandatory_exclude_ciphers</a>
(default: empty)</b></DT><DD>

<p> Additional list of ciphers or cipher types to exclude from the
SMTP client cipher list at mandatory TLS security levels. This list
works in addition to the exclusions listed with <a href="postconf.5.html#smtp_tls_exclude_ciphers">smtp_tls_exclude_ciphers</a>
(see there for syntax details).  </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="smtp_tls_mandatory_protocols">smtp_tls_mandatory_protocols</a>
(default: SSLv3, TLSv1)</b></DT><DD>

<p> List of SSL/TLS protocols that the Postfix SMTP client will use with
mandatory TLS encryption.  In <a href="postconf.5.html">main.cf</a> the values are separated by
whitespace, commas or colons. In the policy table "protocols" attribute
(see <a href="postconf.5.html#smtp_tls_policy_maps">smtp_tls_policy_maps</a>) the only valid separator is colon. An
empty value means allow all protocols. The valid protocol names, (see
<b>SSL_get_version(3)</b>), are "SSLv2", "SSLv3" and "TLSv1". </p>

<p> With Postfix &ge; 2.5 the parameter syntax is expanded to support
protocol exclusions. One can now explicitly exclude SSLv2 by setting
"<a href="postconf.5.html#smtp_tls_mandatory_protocols">smtp_tls_mandatory_protocols</a> = !SSLv2". To exclude both SSLv2 and
SSLv3 set "<a href="postconf.5.html#smtp_tls_mandatory_protocols">smtp_tls_mandatory_protocols</a> = !SSLv2, !SSLv3". Listing
the protocols to include, rather than protocols to exclude, is still
supported; use the form you find more intuitive. </p>

<p> Since SSL version 2 has known protocol weaknesses and is now
deprecated, the default setting excludes "SSLv2".  This means that by
default, SSL version 2 will not be used at the "encrypt" security level
and higher. </p>

<p> See the documentation of the <a href="postconf.5.html#smtp_tls_policy_maps">smtp_tls_policy_maps</a> parameter and
<a href="TLS_README.html">TLS_README</a> for more information about security levels. </p>

<p> Example: </p>

<pre>
<a href="postconf.5.html#smtp_tls_mandatory_protocols">smtp_tls_mandatory_protocols</a> = TLSv1
# Alternative form with Postfix &ge; 2.5:
<a href="postconf.5.html#smtp_tls_mandatory_protocols">smtp_tls_mandatory_protocols</a> = !SSLv2, !SSLv3
</pre>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="smtp_tls_note_starttls_offer">smtp_tls_note_starttls_offer</a>
(default: no)</b></DT><DD>

<p> Log the hostname of a remote SMTP server that offers STARTTLS,
when TLS is not already enabled for that server. </p>

<p> The logfile record looks like:  </p>

<pre>
postfix/smtp[pid]:  Host offered STARTTLS: [name.of.host]
</pre>

<p> This feature is available in Postfix 2.2 and later.  </p>


</DD>

<DT><b><a name="smtp_tls_per_site">smtp_tls_per_site</a>
(default: empty)</b></DT><DD>

<p> Optional lookup tables with the Postfix SMTP client TLS usage
policy by next-hop destination and by remote SMTP server hostname.
When both lookups succeed, the more specific per-site policy (NONE,
MUST, etc) overrides the less specific one (MAY), and the more secure
per-site policy (MUST, etc) overrides the less secure one (NONE).
With Postfix 2.3 and later <a href="postconf.5.html#smtp_tls_per_site">smtp_tls_per_site</a> is strongly discouraged:
use <a href="postconf.5.html#smtp_tls_policy_maps">smtp_tls_policy_maps</a> instead. </p>

<p> Use of the bare hostname as the per-site table lookup key is
discouraged. Always use the full destination nexthop (enclosed in
[] with a possible ":port" suffix). A recipient domain or MX-enabled
transport next-hop with no port suffix may look like a bare hostname,
but is still a suitable <i>destination</i>. </p>

<p> Specify a next-hop destination or server hostname on the left-hand
side; no wildcards are allowed. The next-hop destination is either
the recipient domain, or the destination specified with a <a href="transport.5.html">transport(5)</a>
table, the <a href="postconf.5.html#relayhost">relayhost</a> parameter, or the <a href="postconf.5.html#relay_transport">relay_transport</a> parameter.
On the right hand side specify one of the following keywords:  </p>

<dl>

<dt> NONE </dt> <dd> Don't use TLS at all. This overrides a less
specific <b>MAY</b> lookup result from the alternate host or next-hop
lookup key, and overrides the global <a href="postconf.5.html#smtp_use_tls">smtp_use_tls</a>, <a href="postconf.5.html#smtp_enforce_tls">smtp_enforce_tls</a>,
and <a href="postconf.5.html#smtp_tls_enforce_peername">smtp_tls_enforce_peername</a> settings. </dd>

<dt> MAY </dt> <dd> Try to use TLS if the server announces support,
otherwise use the unencrypted connection. This has less precedence
than a more specific result (including <b>NONE</b>) from the alternate
host or next-hop lookup key, and has less precedence than the more
specific global "<a href="postconf.5.html#smtp_enforce_tls">smtp_enforce_tls</a> = yes" or "<a href="postconf.5.html#smtp_tls_enforce_peername">smtp_tls_enforce_peername</a>
= yes".  </dd>

<dt> MUST_NOPEERMATCH </dt> <dd> Require TLS encryption, but do not
require that the remote SMTP server hostname matches the information
in the remote SMTP server certificate, or that the server certificate
was issued by a trusted CA. This overrides a less secure <b>NONE</b>
or a less specific <b>MAY</b> lookup result from the alternate host
or next-hop lookup key, and overrides the global <a href="postconf.5.html#smtp_use_tls">smtp_use_tls</a>,
<a href="postconf.5.html#smtp_enforce_tls">smtp_enforce_tls</a> and <a href="postconf.5.html#smtp_tls_enforce_peername">smtp_tls_enforce_peername</a> settings.  </dd>

<dt> MUST </dt> <dd> Require TLS encryption, require that the remote
SMTP server hostname matches the information in the remote SMTP
server certificate, and require that the remote SMTP server certificate
was issued by a trusted CA. This overrides a less secure <b>NONE</b>
and <b>MUST_NOPEERMATCH</b> or a less specific <b>MAY</b> lookup
result from the alternate host or next-hop lookup key, and overrides
the global <a href="postconf.5.html#smtp_use_tls">smtp_use_tls</a>, <a href="postconf.5.html#smtp_enforce_tls">smtp_enforce_tls</a> and <a href="postconf.5.html#smtp_tls_enforce_peername">smtp_tls_enforce_peername</a>
settings.  </dd>

</dl>

<p> The above keywords correspond to the "none", "may", "encrypt" and
"verify" security levels for the new <a href="postconf.5.html#smtp_tls_security_level">smtp_tls_security_level</a> parameter
introduced in Postfix 2.3. Starting with Postfix 2.3, and independently
of how the policy is specified, the <a href="postconf.5.html#smtp_tls_mandatory_ciphers">smtp_tls_mandatory_ciphers</a> and
<a href="postconf.5.html#smtp_tls_mandatory_protocols">smtp_tls_mandatory_protocols</a> parameters only apply when TLS encryption
is mandatory. Connections for which encryption is optional enable
all "export" grade and better ciphers. </p>

<p> As long as no secure DNS lookup mechanism is available, false
hostnames in MX or CNAME responses can change the server hostname
that Postfix uses for TLS policy lookup and server certificate
verification. Even with a perfect match between the server hostname and
the server certificate, there is no guarantee that Postfix is connected
to the right server.  See <a href="TLS_README.html">TLS_README</a> (Closing a DNS loophole with obsolete
per-site TLS policies) for a possible work-around. </p>

<p> This feature is available in Postfix 2.2 and later. With
Postfix 2.3 and later use <a href="postconf.5.html#smtp_tls_policy_maps">smtp_tls_policy_maps</a> instead. </p>


</DD>

<DT><b><a name="smtp_tls_policy_maps">smtp_tls_policy_maps</a>
(default: empty)</b></DT><DD>

<p> Optional lookup tables with the Postfix SMTP client TLS security
policy by next-hop destination; when a non-empty value is specified,
this overrides the obsolete <a href="postconf.5.html#smtp_tls_per_site">smtp_tls_per_site</a> parameter.  See
<a href="TLS_README.html">TLS_README</a> for a more detailed discussion of TLS security levels.
</p>

<p> The TLS policy table is indexed by the full next-hop destination,
which is either the recipient domain, or the verbatim next-hop
specified in the transport table, $<a href="postconf.5.html#local_transport">local_transport</a>, $<a href="postconf.5.html#virtual_transport">virtual_transport</a>,
$<a href="postconf.5.html#relay_transport">relay_transport</a> or $<a href="postconf.5.html#default_transport">default_transport</a>. This includes any enclosing
square brackets and any non-default destination server port suffix. The
LMTP socket type prefix (inet: or unix:) is not included in the lookup
key. </p>

<p> Only the next-hop domain, or $<a href="postconf.5.html#myhostname">myhostname</a> with LMTP over UNIX-domain
sockets, is used as the nexthop name for certificate verification. The
port and any enclosing square brackets are used in the table lookup key,
but are not used for server name verification. </p>

<p> When the lookup key is a domain name without enclosing square brackets
or any <i>:port</i> suffix (typically the recipient domain), and the full
domain is not found in the table, just as with the <a href="transport.5.html">transport(5)</a> table,
the parent domain starting with a leading "." is matched recursively. This
allows one to specify a security policy for a recipient domain and all
its sub-domains. </p>

<p> The lookup result is a security level, followed by an optional list
of whitespace and/or comma separated name=value attributes that override
related <a href="postconf.5.html">main.cf</a> settings. The TLS security levels in order of increasing
security are: </p>

<dl>

<dt><b>none</b></dt>
<dd>No TLS. No additional attributes are supported at this level. </dd>

<dt><b>may</b></dt>
<dd>Opportunistic TLS. No additional attributes are supported at this
level. Since sending in the clear is acceptable, demanding stronger
than default TLS security parameters merely reduces inter-operability.
Postfix 2.3 and later ignore the <a href="postconf.5.html#smtp_tls_mandatory_ciphers">smtp_tls_mandatory_ciphers</a> and
<a href="postconf.5.html#smtp_tls_mandatory_protocols">smtp_tls_mandatory_protocols</a> parameters at this security level; all
protocols are allowed and "export" grade or better ciphers are used.
When TLS handshakes fail, the connection is retried with TLS disabled.
This allows mail delivery to sites with non-interoperable TLS
implementations.</dd>

<dt><b>encrypt</b></dt> <dd>Mandatory TLS encryption. At this level
and higher the optional "ciphers" attribute overrides the <a href="postconf.5.html">main.cf</a>
<a href="postconf.5.html#smtp_tls_mandatory_ciphers">smtp_tls_mandatory_ciphers</a> parameter and the optional "protocols"
keyword overrides the <a href="postconf.5.html">main.cf</a> <a href="postconf.5.html#smtp_tls_mandatory_protocols">smtp_tls_mandatory_protocols</a> parameter.
In the policy table, multiple protocols must be separated by colons,
as attribute values may not contain whitespace or commas. </dd>

<dt><b>fingerprint</b></dt> <dd>Certificate fingerprint
verification. Available with Postfix 2.5 and later. At this security
level, there are no trusted certificate authorities. The certificate
trust chain, expiration date, ... are not checked. Instead,
the optional <b>match</b> attribute, or else the <a href="postconf.5.html">main.cf</a>
<b><a href="postconf.5.html#smtp_tls_fingerprint_cert_match">smtp_tls_fingerprint_cert_match</a></b> parameter, lists the
valid "fingerprints" of the server certificate. The digest
algorithm used to calculate the fingerprint is selected by the
<b><a href="postconf.5.html#smtp_tls_fingerprint_digest">smtp_tls_fingerprint_digest</a></b> parameter. Multiple fingerprints can
be combined with a "|" delimiter in a single match attribute, or multiple
match attributes can be employed. The ":" character is not used as a
delimiter as it occurs between each pair of fingerprint (hexadecimal)
digits. </dd>

<dt><b>verify</b></dt> <dd>Mandatory TLS verification.  At this security
level, DNS MX lookups are trusted to be secure enough, and the name
verified in the server certificate is usually obtained indirectly via
unauthenticated DNS MX lookups.  The optional "match" attribute overrides
the <a href="postconf.5.html">main.cf</a> <a href="postconf.5.html#smtp_tls_verify_cert_match">smtp_tls_verify_cert_match</a> parameter. In the policy table,
multiple match patterns and strategies must be separated by colons.
In practice explicit control over matching is more common with the
"secure" policy, described below. </dd>

<dt><b>secure</b></dt> <dd>Secure-channel TLS. At this security level, DNS
MX lookups, though potentially used to determine the candidate next-hop
gateway IP addresses, are <b>not</b> trusted to be secure enough for TLS
peername verification. Instead, the default name verified in the server
certificate is obtained directly from the next-hop, or is explicitly
specified via the optional <b>match</b> attribute which overrides the
<a href="postconf.5.html">main.cf</a> <a href="postconf.5.html#smtp_tls_secure_cert_match">smtp_tls_secure_cert_match</a> parameter. In the policy table,
multiple match patterns and strategies must be separated by colons.
The match attribute is most useful when multiple domains are supported by
common server, the policy entries for additional domains specify matching
rules for the primary domain certificate. While transport table overrides
routing the secondary domains to the primary nexthop also allow secure
verification, they risk delivery to the wrong destination when domains
change hands or are re-assigned to new gateways. With the "match"
attribute approach, routing is not perturbed, and mail is deferred if
verification of a new MX host fails. </dd>

</dl>

<p>
Example:
</p>

<pre>
/etc/postfix/<a href="postconf.5.html">main.cf</a>:
    <a href="postconf.5.html#smtp_tls_policy_maps">smtp_tls_policy_maps</a> = hash:/etc/postfix/tls_policy
    # Postfix 2.5 and later
    <a href="postconf.5.html#smtp_tls_fingerprint_digest">smtp_tls_fingerprint_digest</a> = md5
</pre>

<pre>
/etc/postfix/tls_policy:
    example.edu                 none
    example.mil                 may
    example.gov                 encrypt protocols=TLSv1
    example.com                 verify ciphers=high
    example.net                 secure
    .example.net                secure match=.example.net:example.net
    [mail.example.org]:587      secure match=nexthop
    # Postfix 2.5 and later
    [thumb.example.org]          fingerprint
    	match=EC:3B:2D:B0:5B:B1:FB:6D:20:A3:9D:72:F6:8D:12:35
	match=3D:95:34:51:24:66:33:B9:D2:40:99:C0:C1:17:0B:D1
</pre>

<p> <b>Note:</b> The <b>hostname</b> strategy if listed in a non-default
setting of <a href="postconf.5.html#smtp_tls_secure_cert_match">smtp_tls_secure_cert_match</a> or in the <b>match</b> attribute
in the policy table can render the <b>secure</b> level vulnerable to
DNS forgery. Do not use the <b>hostname</b> strategy for secure-channel
configurations in environments where DNS security is not assured. </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="smtp_tls_scert_verifydepth">smtp_tls_scert_verifydepth</a>
(default: 9)</b></DT><DD>

<p> The verification depth for remote SMTP server certificates. A depth
of 1 is sufficient if the issuing CA is listed in a local CA file. </p>

<p> The default verification depth is 9 (the OpenSSL default) for
compatibility with earlier Postfix behavior. Prior to Postfix 2.5,
the default value was 5, but the limit was not actually enforced. If
you have set this to a lower non-default value, certificates with longer
trust chains may now fail to verify. Certificate chains with 1 or 2
CAs are common, deeper chains are more rare and any number between 5
and 9 should suffice in practice. You can choose a lower number if,
for example, you trust certificates directly signed by an issuing CA
but not any CAs it delegates to. </p>

<p> This feature is available in Postfix 2.2 and later.  </p>


</DD>

<DT><b><a name="smtp_tls_secure_cert_match">smtp_tls_secure_cert_match</a>
(default: nexthop, dot-nexthop)</b></DT><DD>

<p> The server certificate peername verification method for the
"secure" TLS security level. In a "secure" TLS policy table
($<a href="postconf.5.html#smtp_tls_policy_maps">smtp_tls_policy_maps</a>) entry the optional "match" attribute
overrides this <a href="postconf.5.html">main.cf</a> setting. </p>

<p> This parameter specifies one or more patterns or strategies separated
by commas, whitespace or colons.  In the policy table the only valid
separator is the colon character. </p>

<p> For a description of the pattern and strategy syntax see the
<a href="postconf.5.html#smtp_tls_verify_cert_match">smtp_tls_verify_cert_match</a> parameter. The "hostname" strategy should
be avoided in this context, as in the absence of a secure global DNS, using
the results of MX lookups in certificate verification is not immune to active
(man-in-the-middle) attacks on DNS. </p>

<p>
Sample <a href="postconf.5.html">main.cf</a> setting:
</p>

<blockquote>
<pre>
<a href="postconf.5.html#smtp_tls_secure_cert_match">smtp_tls_secure_cert_match</a> = nexthop
</pre>
</blockquote>

<p>
Sample policy table override:
</p>

<blockquote>
<pre>
example.net     secure match=example.com:.example.com
.example.net    secure match=example.com:.example.com
</pre>
</blockquote>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="smtp_tls_security_level">smtp_tls_security_level</a>
(default: empty)</b></DT><DD>

<p> The default SMTP TLS security level for the Postfix SMTP client;
when a non-empty value is specified, this overrides the obsolete
parameters <a href="postconf.5.html#smtp_use_tls">smtp_use_tls</a>, <a href="postconf.5.html#smtp_enforce_tls">smtp_enforce_tls</a>, and <a href="postconf.5.html#smtp_tls_enforce_peername">smtp_tls_enforce_peername</a>.
</p>

<p> Specify one of the following security levels: </p>

<dl>

<dt><b>none</b></dt> <dd> TLS will not be used unless enabled for specific
destinations via <a href="postconf.5.html#smtp_tls_policy_maps">smtp_tls_policy_maps</a>. </dd>

<dt><b>may</b></dt>
<dd> Opportunistic TLS. TLS will be used if supported by the server. Since
sending in the clear is acceptable, demanding stronger than default TLS
security parameters merely reduces inter-operability. Postfix 2.3 and
later ignore the <a href="postconf.5.html#smtp_tls_mandatory_ciphers">smtp_tls_mandatory_ciphers</a> and
<a href="postconf.5.html#smtp_tls_mandatory_protocols">smtp_tls_mandatory_protocols</a> parameters at this security level; all
protocols are allowed and "export" grade or better ciphers are used.
When TLS handshakes fail, the connection is retried with TLS disabled.
This allows mail delivery to sites with non-interoperable TLS
implementations. </dd>

<dt><b>encrypt</b></dt> <dd>Mandatory TLS encryption. Since a minimum
level of security is intended, it reasonable to be specific about
sufficiently secure protocol versions and ciphers. At this security level
and higher, the <a href="postconf.5.html">main.cf</a> parameters <a href="postconf.5.html#smtp_tls_mandatory_protocols">smtp_tls_mandatory_protocols</a> and
<a href="postconf.5.html#smtp_tls_mandatory_ciphers">smtp_tls_mandatory_ciphers</a> specify the TLS protocols and minimum
cipher grade which the administrator considers secure enough for
mandatory encrypted sessions. This security level is not an appropriate
default for systems delivering mail to the Internet. </dd>

<dt><b>fingerprint</b></dt> <dd>Certificate fingerprint
verification. Available with Postfix 2.5 and later. At this security
level, there are no trusted certificate authorities. The certificate
trust chain, expiration date, ... are not checked. Instead,
the <b><a href="postconf.5.html#smtp_tls_fingerprint_cert_match">smtp_tls_fingerprint_cert_match</a></b> parameter lists
the valid "fingerprints" of the server certificate. The digest
algorithm used to calculate the fingerprint is selected by the
<b><a href="postconf.5.html#smtp_tls_fingerprint_digest">smtp_tls_fingerprint_digest</a></b> parameter. </dd>

<dt><b>verify</b></dt> <dd>Mandatory TLS verification. At this security
level, DNS MX lookups are trusted to be secure enough, and the name
verified in the server certificate is usually obtained indirectly
via unauthenticated DNS MX lookups. The <a href="postconf.5.html#smtp_tls_verify_cert_match">smtp_tls_verify_cert_match</a>
parameter controls how the server name is verified. In practice explicit
control over matching is more common at the "secure" level, described
below. This security level is not an appropriate default for systems
delivering mail to the Internet. </dd>

<dt><b>secure</b></dt> <dd>Secure-channel TLS.  At this security level,
DNS MX lookups, though potentially used to determine the candidate
next-hop gateway IP addresses, are <b>not</b> trusted to be secure enough
for TLS peername verification. Instead, the default name verified in
the server certificate is obtained from the next-hop domain as specified
in the <a href="postconf.5.html#smtp_tls_secure_cert_match">smtp_tls_secure_cert_match</a> configuration parameter. The default
matching rule is that a server certificate matches when its name is equal
to or is a sub-domain of the nexthop domain. This security level is not
an appropriate default for systems delivering mail to the Internet. </dd>

</dl>

<p>
Examples:
</p>

<pre>
# No TLS. Formerly: <a href="postconf.5.html#smtp_use_tls">smtp_use_tls</a>=no and <a href="postconf.5.html#smtp_enforce_tls">smtp_enforce_tls</a>=no.
<a href="postconf.5.html#smtp_tls_security_level">smtp_tls_security_level</a> = none
</pre>

<pre>
# Opportunistic TLS.
<a href="postconf.5.html#smtp_tls_security_level">smtp_tls_security_level</a> = may
</pre>

<pre>
# Mandatory (high-grade) TLS encryption.
<a href="postconf.5.html#smtp_tls_security_level">smtp_tls_security_level</a> = encrypt
<a href="postconf.5.html#smtp_tls_mandatory_ciphers">smtp_tls_mandatory_ciphers</a> = high
</pre>

<pre>
# Mandatory TLS verification of hostname or nexthop domain.
<a href="postconf.5.html#smtp_tls_security_level">smtp_tls_security_level</a> = verify
<a href="postconf.5.html#smtp_tls_mandatory_ciphers">smtp_tls_mandatory_ciphers</a> = high
<a href="postconf.5.html#smtp_tls_verify_cert_match">smtp_tls_verify_cert_match</a> = hostname, nexthop, dot-nexthop
</pre>

<pre>
# Secure channel TLS with exact nexthop name match.
<a href="postconf.5.html#smtp_tls_security_level">smtp_tls_security_level</a> = secure
<a href="postconf.5.html#smtp_tls_mandatory_protocols">smtp_tls_mandatory_protocols</a> = TLSv1
<a href="postconf.5.html#smtp_tls_mandatory_ciphers">smtp_tls_mandatory_ciphers</a> = high
<a href="postconf.5.html#smtp_tls_secure_cert_match">smtp_tls_secure_cert_match</a> = nexthop
</pre>

<pre>
# Certificate fingerprint verification (Postfix &ge; 2.5).
# The CA-less "fingerprint" security level only scales to a limited
# number of destinations. As a global default rather than a per-site
# setting, this is practical when mail for all recipients is sent
# to a central mail hub.
<a href="postconf.5.html#relayhost">relayhost</a> = [mailhub.example.com]
<a href="postconf.5.html#smtp_tls_security_level">smtp_tls_security_level</a> = fingerprint
<a href="postconf.5.html#smtp_tls_mandatory_protocols">smtp_tls_mandatory_protocols</a> = !SSLv2, !SSLv3
<a href="postconf.5.html#smtp_tls_mandatory_ciphers">smtp_tls_mandatory_ciphers</a> = high
<a href="postconf.5.html#smtp_tls_fingerprint_cert_match">smtp_tls_fingerprint_cert_match</a> =
    3D:95:34:51:24:66:33:B9:D2:40:99:C0:C1:17:0B:D1
    EC:3B:2D:B0:5B:B1:FB:6D:20:A3:9D:72:F6:8D:12:35
</pre>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="smtp_tls_session_cache_database">smtp_tls_session_cache_database</a>
(default: empty)</b></DT><DD>

<p> Name of the file containing the optional Postfix SMTP client
TLS session cache. Specify a database type that supports enumeration,
such as <b>btree</b> or <b>sdbm</b>; there is no need to support
concurrent access.  The file is created if it does not exist. The <a href="smtp.8.html">smtp(8)</a>
daemon does not use this parameter directly, rather the cache is
implemented indirectly in the <a href="tlsmgr.8.html">tlsmgr(8)</a> daemon. This means that
per-smtp-instance <a href="master.5.html">master.cf</a> overrides of this parameter are not effective.
Note, that each of the cache databases supported by <a href="tlsmgr.8.html">tlsmgr(8)</a> daemon:
$<a href="postconf.5.html#smtpd_tls_session_cache_database">smtpd_tls_session_cache_database</a>, $<a href="postconf.5.html#smtp_tls_session_cache_database">smtp_tls_session_cache_database</a>
(and with Postfix 2.3 and later $<a href="postconf.5.html#lmtp_tls_session_cache_database">lmtp_tls_session_cache_database</a>), needs to
be stored separately. It is not at this time possible to store multiple
caches in a single database. </p>

<p> Note: <b>dbm</b> databases are not suitable. TLS
session objects are too large. </p>

<p> As of version 2.5, Postfix no longer uses root privileges when
opening this file. The file should now be stored under the Postfix-owned
<a href="postconf.5.html#data_directory">data_directory</a>. As a migration aid, an attempt to open the file
under a non-Postfix directory is redirected to the Postfix-owned
<a href="postconf.5.html#data_directory">data_directory</a>, and a warning is logged. </p>

<p> Example: </p>

<pre>
<a href="postconf.5.html#smtp_tls_session_cache_database">smtp_tls_session_cache_database</a> = btree:/var/lib/postfix/smtp_scache
</pre>

<p> This feature is available in Postfix 2.2 and later.  </p>


</DD>

<DT><b><a name="smtp_tls_session_cache_timeout">smtp_tls_session_cache_timeout</a>
(default: 3600s)</b></DT><DD>

<p> The expiration time of Postfix SMTP client TLS session cache
information.  A cache cleanup is performed periodically
every $<a href="postconf.5.html#smtp_tls_session_cache_timeout">smtp_tls_session_cache_timeout</a> seconds. As with
$<a href="postconf.5.html#smtp_tls_session_cache_database">smtp_tls_session_cache_database</a>, this parameter is implemented in the
<a href="tlsmgr.8.html">tlsmgr(8)</a> daemon and therefore per-smtp-instance <a href="master.5.html">master.cf</a> overrides
are not possible. </p>

<p> This feature is available in Postfix 2.2 and later.  </p>


</DD>

<DT><b><a name="smtp_tls_verify_cert_match">smtp_tls_verify_cert_match</a>
(default: hostname)</b></DT><DD>

<p> The server certificate peername verification method for the
"verify" TLS security level. In a "verify" TLS policy table
($<a href="postconf.5.html#smtp_tls_policy_maps">smtp_tls_policy_maps</a>) entry the optional "match" attribute
overrides this <a href="postconf.5.html">main.cf</a> setting. </p>

<p> This parameter specifies one or more patterns or strategies separated
by commas, whitespace or colons.  In the policy table the only valid
separator is the colon character. </p>

<p> Patterns specify domain names, or domain name suffixes: </p>

<dl>

<dt><i>example.com</i></dt> <dd> Match the <i>example.com</i> domain,
i.e. one of the names the server certificate must be <i>example.com</i>,
upper and lower case distinctions are ignored. </dd>

<dt><i>.example.com</i></dt>
<dd> Match subdomains of the <i>example.com</i> domain, i.e. match
a name in the server certificate that consists of a non-zero number of
labels followed by a <i>.example.com</i> suffix. Case distinctions are
ignored.</dd>

</dl>

<p> Strategies specify a transformation from the next-hop domain
to the expected name in the server certificate: </p>

<dl>

<dt>nexthop</dt>
<dd> Match against the next-hop domain, which is either the recipient
domain, or the transport next-hop configured for the domain stripped of
any optional socket type prefix, enclosing square brackets and trailing
port. When MX lookups are not suppressed, this is the original nexthop
domain prior to the MX lookup, not the result of the MX lookup. For
LMTP delivery via UNIX-domain sockets, the verified next-hop name is
$<a href="postconf.5.html#myhostname">myhostname</a>.  This strategy is suitable for use with the "secure"
policy. Case is ignored.</dd>

<dt>dot-nexthop</dt>
<dd> As above, but match server certificate names that are subdomains
of the next-hop domain. Case is ignored.</dd>

<dt>hostname</dt> <dd> Match against the hostname of the server, often
obtained via an unauthenticated DNS MX lookup. For LMTP delivery via
UNIX-domain sockets, the verified name is $<a href="postconf.5.html#myhostname">myhostname</a>. This matches
the verification strategy of the "MUST" keyword in the obsolete
<a href="postconf.5.html#smtp_tls_per_site">smtp_tls_per_site</a> table, and is suitable for use with the "verify"
security level. When the next-hop name is enclosed in square brackets
to suppress MX lookups, the "hostname" strategy is the same as the
"nexthop" strategy. Case is ignored.</dd>

</dl>

<p>
Sample <a href="postconf.5.html">main.cf</a> setting:
</p>

<pre>
<a href="postconf.5.html#smtp_tls_verify_cert_match">smtp_tls_verify_cert_match</a> = hostname, nexthop, dot-nexthop
</pre>

<p>
Sample policy table override:
</p>

<pre>
example.com     verify  match=hostname:nexthop
.example.com    verify  match=example.com:.example.com:hostname
</pre>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="smtp_use_tls">smtp_use_tls</a>
(default: no)</b></DT><DD>

<p> Opportunistic mode: use TLS when a remote SMTP server announces
STARTTLS support, otherwise send the mail in the clear. Beware:
some SMTP servers offer STARTTLS even if it is not configured.  With
Postfix &lt; 2.3, if the TLS handshake fails, and no other server is
available, delivery is deferred and mail stays in the queue. If this
is a concern for you, use the <a href="postconf.5.html#smtp_tls_per_site">smtp_tls_per_site</a> feature instead.  </p>

<p> This feature is available in Postfix 2.2 and later. With
Postfix 2.3 and later use <a href="postconf.5.html#smtp_tls_security_level">smtp_tls_security_level</a> instead. </p>


</DD>

<DT><b><a name="smtp_xforward_timeout">smtp_xforward_timeout</a>
(default: 300s)</b></DT><DD>

<p>
The SMTP client time limit for sending the XFORWARD command, and
for receiving the server response.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>


</DD>

<DT><b><a name="smtpd_authorized_verp_clients">smtpd_authorized_verp_clients</a>
(default: $<a href="postconf.5.html#authorized_verp_clients">authorized_verp_clients</a>)</b></DT><DD>

<p> What SMTP clients are allowed to specify the XVERP command.
This command requests that mail be delivered one recipient at a
time with a per recipient return address.  </p>

<p> By default, no clients are allowed to specify XVERP.  </p>

<p> This parameter was renamed with Postfix version 2.1. The default value
is backwards compatible with Postfix version 2.0.  </p>

<p> Specify a list of network/netmask patterns, separated by commas
and/or whitespace. The mask specifies the number of bits in the
network part of a host address. You can also specify hostnames or
.domain names (the initial dot causes the domain to match any name
below it),  "/file/name" or "<a href="DATABASE_README.html">type:table</a>" patterns.  A "/file/name"
pattern is replaced by its contents; a "<a href="DATABASE_README.html">type:table</a>" lookup table
is matched when a table entry matches a lookup string (the lookup
result is ignored).  Continue long lines by starting the next line
with whitespace. Specify "!pattern" to exclude an address or network
block from the list. The form "!/file/name" is supported only in
Postfix version 2.4 and later.  </p>

<p> Note: IP version 6 address information must be specified inside
<tt>[]</tt> in the <a href="postconf.5.html#smtpd_authorized_verp_clients">smtpd_authorized_verp_clients</a> value, and in
files specified with "/file/name".  IP version 6 addresses contain
the ":" character, and would otherwise be confused with a "<a href="DATABASE_README.html">type:table</a>"
pattern.  </p>


</DD>

<DT><b><a name="smtpd_authorized_xclient_hosts">smtpd_authorized_xclient_hosts</a>
(default: empty)</b></DT><DD>

<p>
What SMTP clients are allowed to use the XCLIENT feature.  This
command overrides SMTP client information that is used for access
control. Typical use is for SMTP-based content filters, fetchmail-like
programs, or SMTP server access rule testing. See the <a href="XCLIENT_README.html">XCLIENT_README</a>
document for details.
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>

<p>
By default, no clients are allowed to specify XCLIENT.
</p>

<p>
Specify a list of network/netmask patterns, separated by commas
and/or whitespace. The mask specifies the number of bits in the
network part of a host address. You can also specify hostnames or
.domain names (the initial dot causes the domain to match any name
below it),  "/file/name" or "<a href="DATABASE_README.html">type:table</a>" patterns.  A "/file/name"
pattern is replaced by its contents; a "<a href="DATABASE_README.html">type:table</a>" lookup table
is matched when a table entry matches a lookup string (the lookup
result is ignored).  Continue long lines by starting the next line
with whitespace. Specify "!pattern" to exclude an address or network
block from the list. The form "!/file/name" is supported only in
Postfix version 2.4 and later.  </p>

<p> Note: IP version 6 address information must be specified inside
<tt>[]</tt> in the <a href="postconf.5.html#smtpd_authorized_xclient_hosts">smtpd_authorized_xclient_hosts</a> value, and in
files specified with "/file/name".  IP version 6 addresses contain
the ":" character, and would otherwise be confused with a "<a href="DATABASE_README.html">type:table</a>"
pattern.  </p>


</DD>

<DT><b><a name="smtpd_authorized_xforward_hosts">smtpd_authorized_xforward_hosts</a>
(default: empty)</b></DT><DD>

<p>
What SMTP clients are allowed to use the XFORWARD feature.  This
command forwards information that is used to improve logging after
SMTP-based content filters. See the <a href="XFORWARD_README.html">XFORWARD_README</a> document for
details.
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>

<p>
By default, no clients are allowed to specify XFORWARD.
</p>

<p>
Specify a list of network/netmask patterns, separated by commas
and/or whitespace. The mask specifies the number of bits in the
network part of a host address. You can also specify hostnames or
.domain names (the initial dot causes the domain to match any name
below it),  "/file/name" or "<a href="DATABASE_README.html">type:table</a>" patterns.  A "/file/name"
pattern is replaced by its contents; a "<a href="DATABASE_README.html">type:table</a>" lookup table
is matched when a table entry matches a lookup string (the lookup
result is ignored).  Continue long lines by starting the next line
with whitespace. Specify "!pattern" to exclude an address or network
block from the list. The form "!/file/name" is supported only in
Postfix version 2.4 and later.  </p>

<p> Note: IP version 6 address information must be specified inside
<tt>[]</tt> in the <a href="postconf.5.html#smtpd_authorized_xforward_hosts">smtpd_authorized_xforward_hosts</a> value, and in
files specified with "/file/name".  IP version 6 addresses contain
the ":" character, and would otherwise be confused with a "<a href="DATABASE_README.html">type:table</a>"
pattern.  </p>


</DD>

<DT><b><a name="smtpd_banner">smtpd_banner</a>
(default: $<a href="postconf.5.html#myhostname">myhostname</a> ESMTP $<a href="postconf.5.html#mail_name">mail_name</a>)</b></DT><DD>

<p>
The text that follows the 220 status code in the SMTP greeting
banner. Some people like to see the mail version advertised. By
default, Postfix shows no version.
</p>

<p>
You MUST specify $<a href="postconf.5.html#myhostname">myhostname</a> at the start of the text. This is
required by the SMTP protocol.
</p>

<p>
Example:
</p>

<pre>
<a href="postconf.5.html#smtpd_banner">smtpd_banner</a> = $<a href="postconf.5.html#myhostname">myhostname</a> ESMTP $<a href="postconf.5.html#mail_name">mail_name</a> ($<a href="postconf.5.html#mail_version">mail_version</a>)
</pre>


</DD>

<DT><b><a name="smtpd_client_connection_count_limit">smtpd_client_connection_count_limit</a>
(default: 50)</b></DT><DD>

<p>
How many simultaneous connections any client is allowed to
make to this service.  By default, the limit is set to half
the default process limit value.
</p>

<p>
To disable this feature, specify a limit of 0.
</p>

<p>
WARNING: The purpose of this feature is to limit abuse. It must
not be used to regulate legitimate mail traffic.
</p>

<p>
This feature is available in Postfix 2.2 and later.
</p>


</DD>

<DT><b><a name="smtpd_client_connection_rate_limit">smtpd_client_connection_rate_limit</a>
(default: 0)</b></DT><DD>

<p>
The maximal number of connection attempts any client is allowed to
make to this service per time unit.  The time unit is specified
with the <a href="postconf.5.html#anvil_rate_time_unit">anvil_rate_time_unit</a> configuration parameter.
</p>

<p>
By default, a client can make as many connections per time unit as
Postfix can accept.
</p>

<p>
To disable this feature, specify a limit of 0.
</p>

<p>
WARNING: The purpose of this feature is to limit abuse. It must
not be used to regulate legitimate mail traffic.
</p>

<p>
This feature is available in Postfix 2.2 and later.
</p>

<p>
Example:
</p>

<pre>
<a href="postconf.5.html#smtpd_client_connection_rate_limit">smtpd_client_connection_rate_limit</a> = 1000
</pre>


</DD>

<DT><b><a name="smtpd_client_event_limit_exceptions">smtpd_client_event_limit_exceptions</a>
(default: $<a href="postconf.5.html#mynetworks">mynetworks</a>)</b></DT><DD>

<p>
Clients that are excluded from connection count, connection rate,
or SMTP request rate restrictions. See the <a href="postconf.5.html#mynetworks">mynetworks</a> parameter
description for the parameter value syntax.
</p>

<p>
By default, clients in trusted networks are excluded. Specify a
list of network blocks, hostnames or .domain names (the initial
dot causes the domain to match any name below it).
</p>

<p> Note: IP version 6 address information must be specified inside
<tt>[]</tt> in the <a href="postconf.5.html#smtpd_client_event_limit_exceptions">smtpd_client_event_limit_exceptions</a> value, and
in files specified with "/file/name".  IP version 6 addresses
contain the ":" character, and would otherwise be confused with a
"<a href="DATABASE_README.html">type:table</a>" pattern.  </p>

<p>
This feature is available in Postfix 2.2 and later.
</p>


</DD>

<DT><b><a name="smtpd_client_message_rate_limit">smtpd_client_message_rate_limit</a>
(default: 0)</b></DT><DD>

<p>
The maximal number of message delivery requests that any client is
allowed to make to this service per time unit, regardless of whether
or not Postfix actually accepts those messages.  The time unit is
specified with the <a href="postconf.5.html#anvil_rate_time_unit">anvil_rate_time_unit</a> configuration parameter.
</p>

<p>
By default, a client can send as many message delivery requests
per time unit as Postfix can accept.
</p>

<p>
To disable this feature, specify a limit of 0.
</p>

<p>
WARNING: The purpose of this feature is to limit abuse. It must
not be used to regulate legitimate mail traffic.
</p>

<p>
This feature is available in Postfix 2.2 and later.
</p>

<p>
Example:
</p>

<pre>
<a href="postconf.5.html#smtpd_client_message_rate_limit">smtpd_client_message_rate_limit</a> = 1000
</pre>


</DD>

<DT><b><a name="smtpd_client_new_tls_session_rate_limit">smtpd_client_new_tls_session_rate_limit</a>
(default: 0)</b></DT><DD>

<p>
The maximal number of new (i.e., uncached) TLS sessions that a
remote SMTP client is allowed to negotiate with this service per
time unit.  The time unit is specified with the <a href="postconf.5.html#anvil_rate_time_unit">anvil_rate_time_unit</a>
configuration parameter.
</p>

<p>
By default, a remote SMTP client can negotiate as many new TLS
sessions per time unit as Postfix can accept.
</p>

<p>
To disable this feature, specify a limit of 0. Otherwise, specify
a limit that is at least the per-client concurrent session limit,
or else legitimate client sessions may be rejected.
</p>

<p>
WARNING: The purpose of this feature is to limit abuse. It must
not be used to regulate legitimate mail traffic.
</p>

<p>
This feature is available in Postfix 2.3 and later.
</p>

<p>
Example:
</p>

<pre>
<a href="postconf.5.html#smtpd_client_new_tls_session_rate_limit">smtpd_client_new_tls_session_rate_limit</a> = 100
</pre>


</DD>

<DT><b><a name="smtpd_client_port_logging">smtpd_client_port_logging</a>
(default: no)</b></DT><DD>

<p> Enable logging of the remote SMTP client port in addition to
the hostname and IP address. The logging format is "host[address]:port".
</p>

<p> This feature is available in Postfix 2.5 and later. </p>


</DD>

<DT><b><a name="smtpd_client_recipient_rate_limit">smtpd_client_recipient_rate_limit</a>
(default: 0)</b></DT><DD>

<p>
The maximal number of recipient addresses that any client is allowed
to send to this service per time unit, regardless of whether or not
Postfix actually accepts those recipients.  The time unit is specified
with the <a href="postconf.5.html#anvil_rate_time_unit">anvil_rate_time_unit</a> configuration parameter.
</p>

<p>
By default, a client can make as many recipient addresses per time
unit as Postfix can accept.
</p>

<p>
To disable this feature, specify a limit of 0.
</p>

<p>
WARNING: The purpose of this feature is to limit abuse. It must
not be used to regulate legitimate mail traffic.
</p>

<p>
This feature is available in Postfix 2.2 and later.
</p>

<p>
Example:
</p>

<pre>
<a href="postconf.5.html#smtpd_client_recipient_rate_limit">smtpd_client_recipient_rate_limit</a> = 1000
</pre>


</DD>

<DT><b><a name="smtpd_client_restrictions">smtpd_client_restrictions</a>
(default: empty)</b></DT><DD>

<p>
Optional SMTP server access restrictions in the context of a client
SMTP connection request.
</p>

<p>
The default is to allow all connection requests.
</p>

<p>
Specify a list of restrictions, separated by commas and/or whitespace.
Continue long lines by starting the next line with whitespace.
Restrictions are applied in the order as specified; the first
restriction that matches wins.
</p>

<p>
The following restrictions are specific to client hostname or
client network address information.
</p>

<dl>

<dt><b><a name="check_ccert_access">check_ccert_access</a> <i><a href="DATABASE_README.html">type:table</a></i></b></dt>

<dd> Use the client certificate fingerprint as lookup key for the
specified <a href="access.5.html">access(5)</a> database; with Postfix version 2.2, also require that
the SMTP client certificate is verified successfully.
The fingerprint digest algorithm is configurable via the
<a href="postconf.5.html#smtpd_tls_fingerprint_digest">smtpd_tls_fingerprint_digest</a> parameter (hard-coded as md5 prior to
Postfix version 2.5).  This feature is available with Postfix version
2.2 and later. </dd>

<dt><b><a name="check_client_access">check_client_access</a> <i><a href="DATABASE_README.html">type:table</a></i></b></dt>

<dd>Search the specified access database for the client hostname,
parent domains, client IP address, or networks obtained by stripping
least significant octets. See the <a href="access.5.html">access(5)</a> manual page for details. </dd>

<dt><b><a name="permit_inet_interfaces">permit_inet_interfaces</a></b></dt>

<dd>Permit the request when the client IP address matches
$<a href="postconf.5.html#inet_interfaces">inet_interfaces</a>. </dd>

<dt><b><a name="permit_mynetworks">permit_mynetworks</a></b></dt>

<dd>Permit the request when the client IP address matches any
network or network address listed in  $<a href="postconf.5.html#mynetworks">mynetworks</a>. </dd>

<dt><b><a name="permit_sasl_authenticated">permit_sasl_authenticated</a></b></dt>

<dd> Permit the request when the client is successfully
authenticated via the <a href="http://tools.ietf.org/html/rfc4954">RFC 4954</a> (AUTH) protocol. </dd>

<dt><b><a name="permit_tls_all_clientcerts">permit_tls_all_clientcerts</a></b></dt>

<dd> Permit the request when the remote SMTP client certificate is
verified successfully.  This option must be used only if a special
CA issues the certificates and only this CA is listed as trusted
CA, otherwise all clients with a recognized certificate would be
allowed to relay. This feature is available with Postfix version 2.2.</dd>

<dt><b><a name="permit_tls_clientcerts">permit_tls_clientcerts</a></b></dt>

<dd>Permit the request when the remote SMTP client certificate
fingerprint is listed in $<a href="postconf.5.html#relay_clientcerts">relay_clientcerts</a>.
The fingerprint digest algorithm is configurable via the
<a href="postconf.5.html#smtpd_tls_fingerprint_digest">smtpd_tls_fingerprint_digest</a> parameter (hard-coded as md5 prior to
Postfix version 2.5).  This feature is available with Postfix version
2.2. </dd>

<dt><b><a name="reject_rbl_client">reject_rbl_client <i>rbl_domain=d.d.d.d</i></a></b></dt>

<dd>Reject the request when the reversed client network address is
listed with the A record "<i>d.d.d.d</i>" under <i>rbl_domain</i>
(Postfix version 2.1 and later only).  If no "<i>=d.d.d.d</i>" is
specified, reject the request when the reversed client network
address is listed with any A record under <i>rbl_domain</i>. <br>
The <a href="postconf.5.html#maps_rbl_reject_code">maps_rbl_reject_code</a> parameter specifies the response code for
rejected requests (default:  554), the <a href="postconf.5.html#default_rbl_reply">default_rbl_reply</a>  parameter
specifies the default server reply, and the <a href="postconf.5.html#rbl_reply_maps">rbl_reply_maps</a>  parameter
specifies tables with server replies indexed by <i>rbl_domain</i>.
This feature is available in Postfix 2.0 and later.  </dd>

<dt><b><a name="reject_rhsbl_client">reject_rhsbl_client <i>rbl_domain=d.d.d.d</i></a></b></dt>

<dd>Reject the request when the client hostname is listed with the
A record "<i>d.d.d.d</i>" under <i>rbl_domain</i> (Postfix version
2.1 and later only).  If no "<i>=d.d.d.d</i>" is specified, reject
the request when the client hostname is listed with
any A record under <i>rbl_domain</i>. See the <a href="postconf.5.html#reject_rbl_client">reject_rbl_client</a>
description above for additional RBL related configuration parameters.
This feature is available in Postfix 2.0 and later.  </dd>

<dt><b><a name="reject_unknown_client_hostname">reject_unknown_client_hostname</a></b> (with Postfix &lt; 2.3: reject_unknown_client)</dt>

<dd>Reject the request when 1) the client IP address-&gt;name mapping
fails, 2) the name-&gt;address mapping fails, or 3) the name-&gt;address
mapping does not match the client IP address.  <br> This is a
stronger restriction than the <a href="postconf.5.html#reject_unknown_reverse_client_hostname">reject_unknown_reverse_client_hostname</a>
feature, which triggers only under condition 1) above. <br> The
<a href="postconf.5.html#unknown_client_reject_code">unknown_client_reject_code</a> parameter specifies the response code
for rejected requests (default: 450). The reply is always 450 in
case the address-&gt;name or name-&gt;address lookup failed due to
a temporary problem. </dd>

<dt><b><a name="reject_unknown_reverse_client_hostname">reject_unknown_reverse_client_hostname</a></b></dt>

<dd>Reject the request when the client IP address has no address-&gt;name
mapping. <br> This is a weaker restriction than the
<a href="postconf.5.html#reject_unknown_client_hostname">reject_unknown_client_hostname</a> feature, which requires not only
that the address-&gt;name and name-&gt;address mappings exist, but
also that the two mappings reproduce the client IP address.  <br>
The <a href="postconf.5.html#unknown_client_reject_code">unknown_client_reject_code</a> parameter specifies the response
code for rejected requests (default: 450).  The reply is always 450
in case the address-&gt;name lookup failed due to a temporary
problem. <br> This feature is available in Postfix 2.3 and
later.  </dd>

</dl>

<p>
In addition, you can use any of the following <a name="generic">
generic</a> restrictions.  These restrictions are applicable in
any SMTP command context.
</p>

<dl>

<dt><b><a name="check_policy_service">check_policy_service <i>servername</i></a></b></dt>

<dd>Query the specified policy server. See the <a href="SMTPD_POLICY_README.html">SMTPD_POLICY_README</a>
document for details. This feature is available in Postfix 2.1
and later. </dd>

<dt><b><a name="defer">defer</a></b></dt>

<dd>Defer the request. The client is told to try again later. This
restriction is useful at the end of a restriction list, to make
the default policy explicit. <br> The <a href="postconf.5.html#defer_code">defer_code</a> parameter specifies
the SMTP server reply code (default: 450).</dd>

<dt><b><a name="defer_if_permit">defer_if_permit</a></b></dt>

<dd>Defer the request if some later restriction would result in an
explicit or implicit PERMIT action.  This is useful when a blacklisting
feature fails due to a temporary problem.  This feature is available
in Postfix version 2.1 and later.  </dd>

<dt><b><a name="defer_if_reject">defer_if_reject</a></b></dt>

<dd>Defer the request if some later restriction would result in a
REJECT action.  This is useful when a whitelisting feature fails
due to a temporary problem.  This feature is available in Postfix
version 2.1 and later.  </dd>

<dt><b><a name="permit">permit</a></b></dt>

<dd>Permit the request. This restriction is useful at the end of
a restriction list, to make the default policy explicit.</dd>

<dt><b><a name="reject_multi_recipient_bounce">reject_multi_recipient_bounce</a></b></dt>

<dd>Reject the request when the envelope sender is the null address,
and the message has multiple envelope recipients. This usage has
rare but legitimate applications: under certain conditions,
multi-recipient mail that was posted with the DSN option NOTIFY=NEVER
may be forwarded with the null sender address.
<br> Note: this restriction can only work reliably
when used in <a href="postconf.5.html#smtpd_data_restrictions">smtpd_data_restrictions</a> or
<a href="postconf.5.html#smtpd_end_of_data_restrictions">smtpd_end_of_data_restrictions</a>, because the total number of
recipients is not known at an earlier stage of the SMTP conversation.
Use at the RCPT stage will only reject the second etc.  recipient.
<br>
The <a href="postconf.5.html#multi_recipient_bounce_reject_code">multi_recipient_bounce_reject_code</a> parameter specifies the
response code for rejected requests (default:  550).  This feature
is available in Postfix 2.1 and later. </dd>

<dt><b><a name="reject_plaintext_session">reject_plaintext_session</a></b></dt>

<dd>Reject the request when the connection is not encrypted. This
restriction should not be used before the client has had a chance
to negotiate encryption with the AUTH or STARTTLS commands.
<br>
The <a href="postconf.5.html#plaintext_reject_code">plaintext_reject_code</a> parameter specifies the response
code for rejected requests (default:  450).  This feature is available
in Postfix 2.3 and later. </dd>

<dt><b><a name="reject_unauth_pipelining">reject_unauth_pipelining</a></b></dt>

<dd>Reject the request when the client sends SMTP commands ahead
of time where it is not allowed, or when the client sends SMTP
commands ahead of time without knowing that Postfix actually supports
ESMTP command pipelining. This stops mail from bulk mail software
that improperly uses ESMTP command pipelining in order to speed up
deliveries. <br> Note: <a href="postconf.5.html#reject_unauth_pipelining">reject_unauth_pipelining</a> is not useful
outside <a href="postconf.5.html#smtpd_data_restrictions">smtpd_data_restrictions</a> when 1) the client uses ESMTP (EHLO
instead of HELO) and 2) with "<a href="postconf.5.html#smtpd_delay_reject">smtpd_delay_reject</a> = yes" (the
default).  The use of <a href="postconf.5.html#reject_unauth_pipelining">reject_unauth_pipelining</a> in the other
restriction contexts is therefore not recommended.  </dd>

<dt><b><a name="reject">reject</a></b></dt>

<dd>Reject the request. This restriction is useful at the end of
a restriction list, to make the default policy explicit.  The
<a href="postconf.5.html#reject_code">reject_code</a> configuration parameter specifies the response code to
rejected requests (default: 554).</dd>

<dt><b><a name="sleep">sleep <i>seconds</i></a></b></dt>

<dd>Pause for the specified number of seconds and proceed with
the next restriction in the list, if any. This may stop zombie
mail when used as:
<pre>
/etc/postfix/<a href="postconf.5.html">main.cf</a>:
    <a href="postconf.5.html#smtpd_client_restrictions">smtpd_client_restrictions</a> =
        sleep 1, <a href="postconf.5.html#reject_unauth_pipelining">reject_unauth_pipelining</a>
    <a href="postconf.5.html#smtpd_delay_reject">smtpd_delay_reject</a> = no
</pre>
This feature is available in Postfix 2.3. </dd>

<dt><b><a name="warn_if_reject">warn_if_reject</a></b></dt>

<dd>Change the meaning of the next restriction, so that it logs
a warning instead of rejecting a request (look for logfile records
that contain "reject_warning"). This is useful for testing new
restrictions in a "live" environment without risking unnecessary
loss of mail. </dd>

</dl>

<p>
Other restrictions that are valid in this context:
</p>

<ul>

<li> SMTP command specific restrictions that are described under
the <a href="postconf.5.html#smtpd_helo_restrictions">smtpd_helo_restrictions</a>, <a href="postconf.5.html#smtpd_sender_restrictions">smtpd_sender_restrictions</a> or
<a href="postconf.5.html#smtpd_recipient_restrictions">smtpd_recipient_restrictions</a> parameters. When helo, sender or
recipient restrictions are listed under <a href="postconf.5.html#smtpd_client_restrictions">smtpd_client_restrictions</a>,
they have effect only with "<a href="postconf.5.html#smtpd_delay_reject">smtpd_delay_reject</a> = yes", so that
$<a href="postconf.5.html#smtpd_client_restrictions">smtpd_client_restrictions</a> is evaluated at the time of the RCPT TO
command.

</ul>

<p>
Example:
</p>

<pre>
<a href="postconf.5.html#smtpd_client_restrictions">smtpd_client_restrictions</a> = <a href="postconf.5.html#permit_mynetworks">permit_mynetworks</a>, <a href="postconf.5.html#reject_unknown_client_hostname">reject_unknown_client_hostname</a>
</pre>


</DD>

<DT><b><a name="smtpd_data_restrictions">smtpd_data_restrictions</a>
(default: empty)</b></DT><DD>

<p>
Optional access restrictions that the Postfix SMTP server applies
in the context of the SMTP DATA command.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>

<p>
Specify a list of restrictions, separated by commas and/or whitespace.
Continue long lines by starting the next line with whitespace.
Restrictions are applied in the order as specified; the first
restriction that matches wins.
</p>

<p>
The following restrictions are valid in this context:
</p>

<ul>

<li><a href="#generic">Generic</a> restrictions that can be used
in any SMTP command context, described under <a href="postconf.5.html#smtpd_client_restrictions">smtpd_client_restrictions</a>.

<li>SMTP command specific restrictions described under
<a href="postconf.5.html#smtpd_client_restrictions">smtpd_client_restrictions</a>, <a href="postconf.5.html#smtpd_helo_restrictions">smtpd_helo_restrictions</a>,
<a href="postconf.5.html#smtpd_sender_restrictions">smtpd_sender_restrictions</a> or <a href="postconf.5.html#smtpd_recipient_restrictions">smtpd_recipient_restrictions</a>.

</ul>

<p>
Examples:
</p>

<pre>
<a href="postconf.5.html#smtpd_data_restrictions">smtpd_data_restrictions</a> = <a href="postconf.5.html#reject_unauth_pipelining">reject_unauth_pipelining</a>
<a href="postconf.5.html#smtpd_data_restrictions">smtpd_data_restrictions</a> = <a href="postconf.5.html#reject_multi_recipient_bounce">reject_multi_recipient_bounce</a>
</pre>


</DD>

<DT><b><a name="smtpd_delay_open_until_valid_rcpt">smtpd_delay_open_until_valid_rcpt</a>
(default: yes)</b></DT><DD>

<p> Postpone the start of an SMTP mail transaction until a valid
RCPT TO command is received. Specify "no" to create a mail transaction
as soon as the SMTP server receives a valid MAIL FROM command. </p>

<p> With sites that reject lots of mail, the default setting reduces
the use of
disk, CPU and memory resources. The downside is that rejected
recipients are logged with NOQUEUE instead of a mail transaction
ID. This complicates the logfile analysis of multi-recipient mail.
</p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="smtpd_delay_reject">smtpd_delay_reject</a>
(default: yes)</b></DT><DD>

<p>
Wait until the RCPT TO command before evaluating
$<a href="postconf.5.html#smtpd_client_restrictions">smtpd_client_restrictions</a>, $<a href="postconf.5.html#smtpd_helo_restrictions">smtpd_helo_restrictions</a> and
$<a href="postconf.5.html#smtpd_sender_restrictions">smtpd_sender_restrictions</a>, or wait until the ETRN command before
evaluating $<a href="postconf.5.html#smtpd_client_restrictions">smtpd_client_restrictions</a> and $<a href="postconf.5.html#smtpd_helo_restrictions">smtpd_helo_restrictions</a>.
</p>

<p>
This feature is turned on by default because some clients apparently
mis-behave when the Postfix SMTP server rejects commands before
RCPT TO.
</p>

<p>
The default setting has one major benefit: it allows Postfix to log
recipient address information when rejecting a client name/address
or sender address, so that it is possible to find out whose mail
is being rejected.
</p>


</DD>

<DT><b><a name="smtpd_discard_ehlo_keyword_address_maps">smtpd_discard_ehlo_keyword_address_maps</a>
(default: empty)</b></DT><DD>

<p> Lookup tables, indexed by the remote SMTP client address, with
case insensitive lists of EHLO keywords (pipelining, starttls, auth,
etc.) that the SMTP server will not send in the EHLO response to a
remote SMTP client. See <a href="postconf.5.html#smtpd_discard_ehlo_keywords">smtpd_discard_ehlo_keywords</a> for details.
The table is not searched by hostname for robustness reasons.  </p>

<p> This feature is available in Postfix 2.2 and later. </p>


</DD>

<DT><b><a name="smtpd_discard_ehlo_keywords">smtpd_discard_ehlo_keywords</a>
(default: empty)</b></DT><DD>

<p> A case insensitive list of EHLO keywords (pipelining, starttls,
auth, etc.) that the SMTP server will not send in the EHLO response
to a remote SMTP client. </p>

<p> This feature is available in Postfix 2.2 and later. </p>

<p> Notes: </p>

<ul>

<li> <p> Specify the <b>silent-discard</b> pseudo keyword to prevent
this action from being logged. </p>

<li> <p> Use the <a href="postconf.5.html#smtpd_discard_ehlo_keyword_address_maps">smtpd_discard_ehlo_keyword_address_maps</a> feature
to discard EHLO keywords selectively.  </p>

</ul>


</DD>

<DT><b><a name="smtpd_end_of_data_restrictions">smtpd_end_of_data_restrictions</a>
(default: empty)</b></DT><DD>

<p> Optional access restrictions that the Postfix SMTP server
applies in the context of the SMTP END-OF-DATA command. </p>

<p> This feature is available in Postfix 2.2 and later. </p>

<p> See <a href="postconf.5.html#smtpd_data_restrictions">smtpd_data_restrictions</a> for syntax details. </p>


</DD>

<DT><b><a name="smtpd_enforce_tls">smtpd_enforce_tls</a>
(default: no)</b></DT><DD>

<p> Mandatory TLS: announce STARTTLS support to SMTP clients,
and require that clients use TLS encryption.  According to <a href="http://tools.ietf.org/html/rfc2487">RFC 2487</a>
this MUST NOT be applied in case of a publicly-referenced SMTP
server.  This option is off by default and should be used only on
dedicated servers. </p>

<p> Note 1: "<a href="postconf.5.html#smtpd_enforce_tls">smtpd_enforce_tls</a> = yes" implies "<a href="postconf.5.html#smtpd_tls_auth_only">smtpd_tls_auth_only</a> = yes". </p>

<p> Note 2: when invoked via "<b>sendmail -bs</b>", Postfix will never offer
STARTTLS due to insufficient privileges to access the server private
key. This is intended behavior. </p>

<p> This feature is available in Postfix 2.2 and later. With
Postfix 2.3 and later use <a href="postconf.5.html#smtpd_tls_security_level">smtpd_tls_security_level</a> instead. </p>


</DD>

<DT><b><a name="smtpd_error_sleep_time">smtpd_error_sleep_time</a>
(default: 1s)</b></DT><DD>

<p>With Postfix version 2.1 and later: the SMTP server response delay after
a client has made more than $<a href="postconf.5.html#smtpd_soft_error_limit">smtpd_soft_error_limit</a> errors, and
fewer than $<a href="postconf.5.html#smtpd_hard_error_limit">smtpd_hard_error_limit</a> errors, without delivering mail.
</p>

<p>With Postfix version 2.0 and earlier: the SMTP server delay before
sending a reject (4xx or 5xx) response, when the client has made
fewer than $<a href="postconf.5.html#smtpd_soft_error_limit">smtpd_soft_error_limit</a> errors without delivering
mail. </p>


</DD>

<DT><b><a name="smtpd_etrn_restrictions">smtpd_etrn_restrictions</a>
(default: empty)</b></DT><DD>

<p>
Optional SMTP server access restrictions in the context of a client
ETRN request.
</p>

<p>
The Postfix ETRN implementation accepts only destinations that are
eligible for the Postfix "fast flush" service. See the <a href="ETRN_README.html">ETRN_README</a>
file for details.
</p>

<p>
Specify a list of restrictions, separated by commas and/or whitespace.
Continue long lines by starting the next line with whitespace.
Restrictions are applied in the order as specified; the first
restriction that matches wins.
</p>

<p>
The following restrictions are specific to the domain name information
received with the ETRN command.
</p>

<dl>

<dt><b><a name="check_etrn_access">check_etrn_access</a> <i><a href="DATABASE_README.html">type:table</a></i></b></dt>

<dd>Search the specified access database for the ETRN domain name
or its parent domains. See the <a href="access.5.html">access(5)</a> manual page for details.
</dd>

</dl>

<p>
Other restrictions that are valid in this context:
</p>

<ul>

<li><a href="#generic">Generic</a> restrictions that can be used
in any SMTP command context, described under <a href="postconf.5.html#smtpd_client_restrictions">smtpd_client_restrictions</a>.

<li>SMTP command specific restrictions described under
<a href="postconf.5.html#smtpd_client_restrictions">smtpd_client_restrictions</a> and <a href="postconf.5.html#smtpd_helo_restrictions">smtpd_helo_restrictions</a>.

</ul>

<p>
Example:
</p>

<pre>
<a href="postconf.5.html#smtpd_etrn_restrictions">smtpd_etrn_restrictions</a> = <a href="postconf.5.html#permit_mynetworks">permit_mynetworks</a>, reject
</pre>


</DD>

<DT><b><a name="smtpd_expansion_filter">smtpd_expansion_filter</a>
(default: see "postconf -d" output)</b></DT><DD>

<p>
What characters are allowed in $name expansions of RBL reply
templates. Characters not in the allowed set are replaced by "_".
Use C like escapes to specify special characters such as whitespace.
</p>

<p>
This parameter is not subjected to $parameter expansion.
</p>

<p>
This feature is available in Postfix 2.0 and later.
</p>


</DD>

<DT><b><a name="smtpd_forbidden_commands">smtpd_forbidden_commands</a>
(default: CONNECT, GET, POST)</b></DT><DD>

<p>
List of commands that causes the Postfix SMTP server to immediately
terminate the session with a 221 code. This can be used to disconnect
clients that obviously attempt to abuse the system. In addition to the
commands listed in this parameter, commands that follow the "Label:"
format of message headers will also cause a disconnect.
</p>

<p>
This feature is available in Postfix 2.2 and later.
</p>


</DD>

<DT><b><a name="smtpd_hard_error_limit">smtpd_hard_error_limit</a>
(default: 20)</b></DT><DD>

<p>
The maximal number of errors a remote SMTP client is allowed to
make without delivering mail. The Postfix SMTP server disconnects
when the limit is exceeded.
</p>


</DD>

<DT><b><a name="smtpd_helo_required">smtpd_helo_required</a>
(default: no)</b></DT><DD>

<p>
Require that a remote SMTP client introduces itself at the beginning
of an SMTP session with the HELO or EHLO command.
</p>

<p>
Example:
</p>

<pre>
<a href="postconf.5.html#smtpd_helo_required">smtpd_helo_required</a> = yes
</pre>


</DD>

<DT><b><a name="smtpd_helo_restrictions">smtpd_helo_restrictions</a>
(default: empty)</b></DT><DD>

<p>
Optional restrictions that the Postfix SMTP server applies in the
context of the SMTP HELO command.
</p>

<p>
The default is to permit everything.
</p>

<p>
Specify a list of restrictions, separated by commas and/or whitespace.
Continue long lines by starting the next line with whitespace.
Restrictions are applied in the order as specified; the first
restriction that matches wins.
</p>

<p>
The following restrictions are specific to the hostname information
received with the HELO or EHLO command.
</p>

<dl>

<dt><b><a name="check_helo_access">check_helo_access</a> <i><a href="DATABASE_README.html">type:table</a></i></b></dt>

<dd>Search the specified <a href="access.5.html">access(5)</a> database for the HELO or EHLO
hostname or parent domains, and execute the corresponding action.
</dd>

<dt><b><a name="check_helo_mx_access">check_helo_mx_access</a> <i><a href="DATABASE_README.html">type:table</a></i></b></dt>

<dd>Search the specified <a href="access.5.html">access(5)</a> database for the MX hosts for
the HELO or EHLO hostname, and execute the corresponding action.
Note: a result of "OK" is not allowed for safety reasons. Instead,
use DUNNO in order to exclude specific hosts from blacklists.  This
feature is available in Postfix 2.1 and later.  </dd>

<dt><b><a name="check_helo_ns_access">check_helo_ns_access</a> <i><a href="DATABASE_README.html">type:table</a></i></b></dt>

<dd>Search the specified <a href="access.5.html">access(5)</a> database for the DNS servers
for the HELO or EHLO hostname, and execute the corresponding action.
Note: a result of "OK" is not allowed for safety reasons. Instead,
use DUNNO in order to exclude specific hosts from blacklists.  This
feature is available in Postfix 2.1 and later.  </dd>

<dt><b><a name="reject_invalid_helo_hostname">reject_invalid_helo_hostname</a></b> (with Postfix &lt; 2.3: reject_invalid_hostname)</dt>

<dd>Reject the request when the HELO or EHLO hostname syntax is
invalid. <br> The <a href="postconf.5.html#invalid_hostname_reject_code">invalid_hostname_reject_code</a> specifies the response
code to rejected requests (default: 501).</dd>

<dt><b><a name="reject_non_fqdn_helo_hostname">reject_non_fqdn_helo_hostname</a></b> (with Postfix &lt; 2.3: reject_non_fqdn_hostname)</dt>

<dd>Reject the request when the HELO or EHLO hostname is not in
fully-qualified domain form, as required by the RFC. <br> The
<a href="postconf.5.html#non_fqdn_reject_code">non_fqdn_reject_code</a> parameter specifies the response code to
rejected requests (default: 504).</dd>

<dt><b><a name="reject_rhsbl_helo">reject_rhsbl_helo <i>rbl_domain=d.d.d.d</i></a></b></dt>

<dd>Reject the request when the HELO or EHLO hostname hostname is
listed with the A record "<i>d.d.d.d</i>" under <i>rbl_domain</i>
(Postfix version 2.1 and later only).  If no "<i>=d.d.d.d</i>" is
specified, reject the request when the HELO or EHLO hostname is
listed with any A record under <i>rbl_domain</i>. See the
<a href="postconf.5.html#reject_rbl_client">reject_rbl_client</a> description for additional RBL related configuration
parameters.  This feature is available in Postfix 2.0 and later.
</dd>

<dt><b><a name="reject_unknown_helo_hostname">reject_unknown_helo_hostname</a></b> (with Postfix &lt; 2.3: reject_unknown_hostname)</dt>

<dd>Reject the request when the HELO or EHLO hostname has no DNS A
or MX record. <br> The <a href="postconf.5.html#unknown_hostname_reject_code">unknown_hostname_reject_code</a> specifies the
response code to rejected requests (default: 450). </dd>

</dl>

<p>
Other restrictions that are valid in this context:
</p>

<ul>

<li> <a href="#generic">Generic</a> restrictions that can be used
in any SMTP command context, described under <a href="postconf.5.html#smtpd_client_restrictions">smtpd_client_restrictions</a>.

<li> Client hostname or network address specific restrictions
described under <a href="postconf.5.html#smtpd_client_restrictions">smtpd_client_restrictions</a>.

<li> SMTP command specific restrictions described under
<a href="postconf.5.html#smtpd_sender_restrictions">smtpd_sender_restrictions</a> or <a href="postconf.5.html#smtpd_recipient_restrictions">smtpd_recipient_restrictions</a>.  When
sender or recipient restrictions are listed under <a href="postconf.5.html#smtpd_helo_restrictions">smtpd_helo_restrictions</a>,
they have effect only with "<a href="postconf.5.html#smtpd_delay_reject">smtpd_delay_reject</a> = yes", so that
$<a href="postconf.5.html#smtpd_helo_restrictions">smtpd_helo_restrictions</a> is evaluated at the time of the RCPT TO
command.

</ul>

<p>
Examples:
</p>

<pre>
<a href="postconf.5.html#smtpd_helo_restrictions">smtpd_helo_restrictions</a> = <a href="postconf.5.html#permit_mynetworks">permit_mynetworks</a>, <a href="postconf.5.html#reject_invalid_helo_hostname">reject_invalid_helo_hostname</a>
<a href="postconf.5.html#smtpd_helo_restrictions">smtpd_helo_restrictions</a> = <a href="postconf.5.html#permit_mynetworks">permit_mynetworks</a>, <a href="postconf.5.html#reject_unknown_helo_hostname">reject_unknown_helo_hostname</a>
</pre>


</DD>

<DT><b><a name="smtpd_history_flush_threshold">smtpd_history_flush_threshold</a>
(default: 100)</b></DT><DD>

<p>
The maximal number of lines in the Postfix SMTP server command history
before it is flushed upon receipt of EHLO, RSET, or end of DATA.
</p>


</DD>

<DT><b><a name="smtpd_junk_command_limit">smtpd_junk_command_limit</a>
(default: 100)</b></DT><DD>

<p>
The number of junk commands (NOOP, VRFY, ETRN or RSET) that a remote
SMTP client can send before the Postfix SMTP server starts to
increment the error counter with each junk command.  The junk
command count is reset after mail is delivered.  See also the
<a href="postconf.5.html#smtpd_error_sleep_time">smtpd_error_sleep_time</a> and <a href="postconf.5.html#smtpd_soft_error_limit">smtpd_soft_error_limit</a> configuration
parameters.
</p>


</DD>

<DT><b><a name="smtpd_milters">smtpd_milters</a>
(default: empty)</b></DT><DD>

<p> A list of Milter (mail filter) applications for new mail that
arrives via the Postfix <a href="smtpd.8.html">smtpd(8)</a> server.  See the <a href="MILTER_README.html">MILTER_README</a>
document for details.  </p>

<p> This feature is available in Postfix 2.3 and later. </p>


</DD>

<DT><b><a name="smtpd_noop_commands">smtpd_noop_commands</a>
(default: empty)</b></DT><DD>

<p>
List of commands that the Postfix SMTP server replies to with "250
Ok", without doing any syntax checks and without changing state.
This list overrides any commands built into the Postfix SMTP server.
</p>


</DD>

<DT><b><a name="smtpd_null_access_lookup_key">smtpd_null_access_lookup_key</a>
(default: &lt;&gt;)</b></DT><DD>

<p>
The lookup key to be used in SMTP <a href="access.5.html">access(5)</a> tables instead of the
null sender address.
</p>


</DD>

<DT><b><a name="smtpd_peername_lookup">smtpd_peername_lookup</a>
(default: yes)</b></DT><DD>

<p> Attempt to look up the remote SMTP client hostname, and verify that
the name matches the client IP address. A client name is set to
"unknown" when it cannot be looked up or verified, or when name
lookup is disabled.  Turning off name lookup reduces delays due to
DNS lookup and increases the maximal inbound delivery rate. </p>

<p> This feature is available in Postfix 2.3 and later.  </p>


</DD>

<DT><b><a name="smtpd_policy_service_max_idle">smtpd_policy_service_max_idle</a>
(default: 300s)</b></DT><DD>

<p>
The time after which an idle SMTPD policy service connection is
closed.
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>


</DD>

<DT><b><a name="smtpd_policy_service_max_ttl">smtpd_policy_service_max_ttl</a>
(default: 1000s)</b></DT><DD>

<p>
The time after which an active SMTPD policy service connection is
closed.
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>


</DD>

<DT><b><a name="smtpd_policy_service_timeout">smtpd_policy_service_timeout</a>
(default: 100s)</b></DT><DD>

<p>
The time limit for connecting to, writing to or receiving from a
delegated SMTPD policy server.
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>


</DD>

<DT><b><a name="smtpd_proxy_ehlo">smtpd_proxy_ehlo</a>
(default: $<a href="postconf.5.html#myhostname">myhostname</a>)</b></DT><DD>

<p>
How the Postfix SMTP server announces itself to the proxy filter.
By default, the Postfix hostname is used.
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>


</DD>

<DT><b><a name="smtpd_proxy_filter">smtpd_proxy_filter</a>
(default: empty)</b></DT><DD>

<p> The hostname and TCP port of the mail filtering proxy server.
The proxy receives all mail from the Postfix SMTP server, and is
supposed to give the result to another Postfix SMTP server process.
</p>

<p> Specify "host:port" or "inet:host:port" for a TCP endpoint, or
"unix:pathname" for a UNIX-domain endpoint. The host can be specified
as an IP address or as a symbolic name; no MX lookups are done.
When no "host" or "host:"  are specified, the local machine is
assumed.  Pathname interpretation is relative to the Postfix queue
directory.  </p>

<p> This feature is available in Postfix 2.1 and later.  </p>

<p> The "inet:" and "unix:" prefixes are available in Postfix 2.3
and later.  </p>


</DD>

<DT><b><a name="smtpd_proxy_timeout">smtpd_proxy_timeout</a>
(default: 100s)</b></DT><DD>

<p>
The time limit for connecting to a proxy filter and for sending or
receiving information.  When a connection fails the client gets a
generic error message while more detailed information is logged to
the maillog file.
</p>

<p>
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).
</p>

<p>
This feature is available in Postfix 2.1 and later.
</p>


</DD>

<DT><b><a name="smtpd_recipient_limit">smtpd_recipient_limit</a>
(default: 1000)</b></DT><DD>

<p>
The maximal number of recipients that the Postfix SMTP server
accepts per message delivery request.
</p>


</DD>

<DT><b><a name="smtpd_recipient_overshoot_limit">smtpd_recipient_overshoot_limit</a>
(default: 1000)</b></DT><DD>

<p> The number of recipients that a remote SMTP client can send in
excess of the limit specified with $<a href="postconf.5.html#smtpd_recipient_limit">smtpd_recipient_limit</a>, before
the Postfix SMTP server increments the per-session error count
for each excess recipient.  </p>


</DD>

<DT><b><a name="smtpd_recipient_restrictions">smtpd_recipient_restrictions</a>
(default: <a href="postconf.5.html#permit_mynetworks">permit_mynetworks</a>, <a href="postconf.5.html#reject_unauth_destination">reject_unauth_destination</a>)</b></DT><DD>

<p>
The access restrictions that the Postfix SMTP server applies in
the context of the RCPT TO command.
</p>

<p>
By default, the Postfix SMTP server accepts:
</p>

<ul>

<li> Mail from clients whose IP address matches $<a href="postconf.5.html#mynetworks">mynetworks</a>, or:

<li> Mail to remote destinations that match $<a href="postconf.5.html#relay_domains">relay_domains</a>, except
for addresses that contain sender-specified routing
(user@elsewhere@domain), or:

<li> Mail to local destinations that match $<a href="postconf.5.html#inet_interfaces">inet_interfaces</a>
or $<a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a>, $<a href="postconf.5.html#mydestination">mydestination</a>, $<a href="postconf.5.html#virtual_alias_domains">virtual_alias_domains</a>, or
$<a href="postconf.5.html#virtual_mailbox_domains">virtual_mailbox_domains</a>.

</ul>

<p>
IMPORTANT: If you change this parameter setting, you must specify
at least one of the following restrictions. Otherwise Postfix will
refuse to receive mail:
</p>

<blockquote>
<pre>
reject, defer, <a href="postconf.5.html#defer_if_permit">defer_if_permit</a>, <a href="postconf.5.html#reject_unauth_destination">reject_unauth_destination</a>
</pre>
</blockquote>

<p>
Specify a list of restrictions, separated by commas and/or whitespace.
Continue long lines by starting the next line with whitespace.
Restrictions are applied in the order as specified; the first
restriction that matches wins.
</p>

<p>
The following restrictions are specific to the recipient address
that is received with the RCPT TO command.
</p>

<dl>

<dt><b><a name="check_recipient_access">check_recipient_access</a> <i><a href="DATABASE_README.html">type:table</a></i></b></dt>

<dd>Search the specified <a href="access.5.html">access(5)</a> database for the resolved RCPT
TO address, domain, parent domains, or localpart@, and execute the
corresponding action.  </dd>

<dt><b><a name="check_recipient_mx_access">check_recipient_mx_access</a> <i><a href="DATABASE_README.html">type:table</a></i></b></dt>

<dd>Search the specified <a href="access.5.html">access(5)</a> database for the MX hosts for
the RCPT TO address, and execute the corresponding action.  Note:
a result of "OK" is not allowed for safety reasons. Instead, use
DUNNO in order to exclude specific hosts from blacklists.  This
feature is available in Postfix 2.1 and later. </dd>

<dt><b><a name="check_recipient_ns_access">check_recipient_ns_access</a> <i><a href="DATABASE_README.html">type:table</a></i></b></dt>

<dd>Search the specified <a href="access.5.html">access(5)</a> database for the DNS servers
for the RCPT TO address, and execute the corresponding action.
Note: a result of "OK" is not allowed for safety reasons. Instead,
use DUNNO in order to exclude specific hosts from blacklists.  This
feature is available in Postfix 2.1 and later.  </dd>

<dt><b><a name="permit_auth_destination">permit_auth_destination</a></b></dt>

<dd>Permit the request when one of the following is true:

<ul>

<li> Postfix is mail forwarder: the resolved RCPT TO address matches
$<a href="postconf.5.html#relay_domains">relay_domains</a> or a subdomain thereof, and the address contains no
sender-specified routing (user@elsewhere@domain),

<li> Postfix is the final destination: the resolved RCPT TO address
matches $<a href="postconf.5.html#mydestination">mydestination</a>, $<a href="postconf.5.html#inet_interfaces">inet_interfaces</a>, $<a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a>,
$<a href="postconf.5.html#virtual_alias_domains">virtual_alias_domains</a>, or $<a href="postconf.5.html#virtual_mailbox_domains">virtual_mailbox_domains</a>, and the address
contains no sender-specified routing (user@elsewhere@domain).

</ul></dd>

<dt><b><a name="permit_mx_backup">permit_mx_backup</a></b></dt>

<dd>Permit the request when the local mail system is backup MX for
the RCPT TO address, or when the address is an authorized destination
(see <a href="postconf.5.html#permit_auth_destination">permit_auth_destination</a> for definition).

<ul>

<li> Safety: <a href="postconf.5.html#permit_mx_backup">permit_mx_backup</a> does not accept addresses that have
sender-specified routing information (example: user@elsewhere@domain).

<li> Safety: <a href="postconf.5.html#permit_mx_backup">permit_mx_backup</a> can be vulnerable to mis-use when
access is not restricted with <a href="postconf.5.html#permit_mx_backup_networks">permit_mx_backup_networks</a>.

<li> Safety: as of Postfix version 2.3, <a href="postconf.5.html#permit_mx_backup">permit_mx_backup</a> no longer
accepts the address when the local mail system is primary MX for
the recipient domain.  Exception: <a href="postconf.5.html#permit_mx_backup">permit_mx_backup</a> accepts the address
when it specifies an authorized destination (see <a href="postconf.5.html#permit_auth_destination">permit_auth_destination</a>
for definition).

<li> Limitation: mail may be rejected in case of a temporary DNS
lookup problem with Postfix prior to version 2.0.

</ul></dd>

<dt><b><a name="reject_non_fqdn_recipient">reject_non_fqdn_recipient</a></b></dt>

<dd>Reject the request when the RCPT TO address is not in
fully-qualified domain form, as required by the RFC. <br> The
<a href="postconf.5.html#non_fqdn_reject_code">non_fqdn_reject_code</a> parameter specifies the response code to
rejected requests (default: 504). </dd>

<dt><b><a name="reject_rhsbl_recipient">reject_rhsbl_recipient <i>rbl_domain=d.d.d.d</i></a></b></dt>

<dd>Reject the request when the RCPT TO domain is listed with the
A record "<i>d.d.d.d</i>" under <i>rbl_domain</i> (Postfix version
2.1 and later only).  If no "<i>=d.d.d.d</i>" is specified, reject
the request when the RCPT TO domain is listed with
any A record under <i>rbl_domain</i>. <br> The <a href="postconf.5.html#maps_rbl_reject_code">maps_rbl_reject_code</a>
parameter specifies the response code for rejected requests (default:
554); the <a href="postconf.5.html#default_rbl_reply">default_rbl_reply</a> parameter specifies the default server
reply; and the <a href="postconf.5.html#rbl_reply_maps">rbl_reply_maps</a> parameter specifies tables with server
replies indexed by <i>rbl_domain</i>.  This feature is available
in Postfix version 2.0 and later.</dd>

<dt><b><a name="reject_unauth_destination">reject_unauth_destination</a></b></dt>

<dd>Reject the request unless one of the following is true:

<ul>

<li> Postfix is mail forwarder: the resolved RCPT TO address matches
$<a href="postconf.5.html#relay_domains">relay_domains</a> or a subdomain thereof, and contains no sender-specified
routing (user@elsewhere@domain),

<li> Postfix is the final destination: the resolved RCPT TO address
matches $<a href="postconf.5.html#mydestination">mydestination</a>, $<a href="postconf.5.html#inet_interfaces">inet_interfaces</a>, $<a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a>,
$<a href="postconf.5.html#virtual_alias_domains">virtual_alias_domains</a>, or $<a href="postconf.5.html#virtual_mailbox_domains">virtual_mailbox_domains</a>, and contains
no sender-specified routing (user@elsewhere@domain).

</ul> The <a href="postconf.5.html#relay_domains_reject_code">relay_domains_reject_code</a> parameter specifies the response
code for rejected requests (default: 554). </dd>

<dt><b><a name="reject_unknown_recipient_domain">reject_unknown_recipient_domain</a></b></dt>

<dd>Reject the request when Postfix is not final destination for
the recipient address, and the RCPT TO address has no DNS A or MX
record, or when it has a malformed MX record such as a record with
a zero-length MX hostname (Postfix version 2.3 and later). <br> The
<a href="postconf.5.html#unknown_address_reject_code">unknown_address_reject_code</a> parameter specifies the response code
for rejected requests (default: 450).  The response is always 450
in case of a temporary DNS error.</dd>

<dt><b><a name="reject_unlisted_recipie