TRANSPORT(5) TRANSPORT(5)
NAME
transport - format of Postfix transport table
SYNOPSIS
postmap /etc/postfix/transport
postmap -q "string" /etc/postfix/transport
postmap -q - /etc/postfix/transport <inputfile
DESCRIPTION
The optional transport table specifies a mapping from
email addresses to message delivery transports and/or
relay hosts. The mapping is used by the trivial-rewrite(8)
daemon.
Normally, the transport table is specified as a text file
that serves as input to the postmap(1) command. The
result, an indexed file in dbm or db format, is used for
fast searching by the mail system. Execute the command
postmap /etc/postfix/transport in order to rebuild the
indexed file after changing the transport table.
When the table is provided via other means such as NIS,
LDAP or SQL, the same lookups are done as for ordinary
indexed files.
Alternatively, the table can be provided as a regular-
expression map where patterns are given as regular expres-
sions. In that case, the lookups are done in a slightly
different way as described in section "REGULAR EXPRESSION
TABLES".
TABLE FORMAT
The format of the transport table is as follows:
pattern result
When pattern matches the recipient address or
domain, use the corresponding result.
blank lines and comments
Empty lines and whitespace-only lines are ignored,
as are lines whose first non-whitespace character
is a `#'.
multi-line text
A logical line starts with non-whitespace text. A
line that starts with whitespace continues a logi-
cal line.
The pattern specifies an email address, a domain name, or
a domain name hierarchy, as described in section "TABLE
LOOKUP".
The result is of the form transport:nexthop. The trans-
port field specifies a mail delivery transport such as
smtp or local. The nexthop field specifies where and how
to deliver mail. More details are given in section "RESULT
FORMAT".
TABLE LOOKUP
With lookups from indexed files such as DB or DBM, or from
networked tables such as NIS, LDAP or SQL, patterns are
tried in the order as listed below:
user+extension@domain transport:nexthop
Mail for user+extension@domain is delivered through
transport to nexthop.
user@domain transport:nexthop
Mail for user@domain is delivered through transport
to nexthop.
domain transport:nexthop
Mail for domain is delivered through transport to
nexthop.
.domain transport:nexthop
Mail for any subdomain of domain is delivered
through transport to nexthop. This applies only
when the string transport_maps is not listed in the
parent_domain_matches_subdomains configuration set-
ting. Otherwise, a domain name matches itself and
its subdomains.
Note 1: the special pattern * represents any address (i.e.
it functions as the wild-card pattern).
Note 2: the null recipient address is looked up as
$empty_address_recipient@$myhostname (default: mailer-dae-
mon@hostname).
RESULT FORMAT
The transport field specifies the name of a mail delivery
transport (the first name of a mail delivery service entry
in the Postfix master.cf file).
The interpretation of the nexthop field is transport
dependent. In the case of SMTP, specify host:service for a
non-default server port, and use [host] or [host]:port in
order to disable MX (mail exchanger) DNS lookups. The []
form is required when you specify an IP address instead of
a hostname.
A null transport and null nexthop result means "do not
change": use the delivery transport and nexthop informa-
tion that would be used when the entire transport table
did not exist.
A non-null transport field with a null nexthop field
resets the nexthop information to the recipient domain.
A null transport field with non-null nexthop field does
not modify the transport information.
EXAMPLES
In order to deliver internal mail directly, while using a
mail relay for all other mail, specify a null entry for
internal destinations (do not change the delivery trans-
port or the nexthop information) and specify a wildcard
for all other destinations.
my.domain :
.my.domain :
* smtp:outbound-relay.my.domain
In order to send mail for foo.org and its subdomains via
the uucp transport to the UUCP host named foo:
foo.org uucp:foo
.foo.org uucp:foo
When no nexthop host name is specified, the destination
domain name is used instead. For example, the following
directs mail for user@foo.org via the slow transport to a
mail exchanger for foo.org. The slow transport could be
something that runs at most one delivery process at a
time:
foo.org slow:
When no transport is specified, Postfix uses the transport
that matches the address domain class (see TRANSPORT FIELD
discussion above). The following sends all mail for
foo.org and its subdomains to host gateway.foo.org:
foo.org :[gateway.foo.org]
.foo.org :[gateway.foo.org]
In the above example, the [] are used to suppress MX
lookups. The result would likely point to your local
machine.
In the case of delivery via SMTP, one may specify host-
name:service instead of just a host:
foo.org smtp:bar.org:2025
This directs mail for user@foo.org to host bar.org port
2025. Instead of a numerical port a symbolic name may be
used. Specify [] around the hostname in order to disable
MX lookups.
The error mailer can be used to bounce mail:
.foo.org error:mail for *.foo.org is not deliv-
erable
This causes all mail for user@anything.foo.org to be
bounced.
REGULAR EXPRESSION TABLES
This section describes how the table lookups change when
the table is given in the form of regular expressions. For
a description of regular expression lookup table syntax,
see regexp_table(5) or pcre_table(5).
Each pattern is a regular expression that is applied to
the entire domain being looked up. Thus, some.domain.hier-
archy is not broken up into parent domains.
Patterns are applied in the order as specified in the
table, until a pattern is found that matches the search
string.
Results are the same as with indexed file lookups, with
the additional feature that parenthesized substrings from
the pattern can be interpolated as $1, $2 and so on.
CONFIGURATION PARAMETERS
The following main.cf parameters are especially relevant
to this topic. See the Postfix main.cf file for syntax
details and for default values. Use the postfix reload
command after a configuration change.
empty_address_recipient
The address that is looked up instead of the null
sender address.
parent_domain_matches_subdomains
List of Postfix features that use domain.tld pat-
terns to match sub.domain.tld (as opposed to
requiring .domain.tld patterns).
transport_maps
List of transport lookup tables.
SEE ALSO
postmap(1) create mapping table
trivial-rewrite(8) rewrite and resolve addresses
pcre_table(5) format of PCRE tables
regexp_table(5) format of POSIX regular expression tables
LICENSE
The Secure Mailer license must be distributed with this
software.
AUTHOR(S)
Wietse Venema
IBM T.J. Watson Research
P.O. Box 704
Yorktown Heights, NY 10598, USA
TRANSPORT(5)