<!doctype html public "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=us-ascii"> <title> Postfix manual - qmgr(8) </title> </head> <body> <pre> QMGR(8) QMGR(8) <b>NAME</b> qmgr - Postfix queue manager <b>SYNOPSIS</b> <b>qmgr</b> [generic Postfix daemon options] <b>DESCRIPTION</b> The <b>qmgr</b> daemon awaits the arrival of incoming mail and arranges for its delivery via Postfix delivery processes. The actual mail routing strategy is delegated to the <a href="trivial-rewrite.8.html"><b>triv-</b></a> <a href="trivial-rewrite.8.html"><b>ial-rewrite</b>(8)</a> daemon. This program expects to be run from the <a href="master.8.html"><b>master</b>(8)</a> process manager. Mail addressed to the local <b>double-bounce</b> address is logged and discarded. This stops potential loops caused by undeliverable bounce notifications. <b>MAIL QUEUES</b> The <b>qmgr</b> daemon maintains the following queues: <b>incoming</b> Inbound mail from the network, or mail picked up by the local <b>pickup</b> agent from the <b>maildrop</b> directory. <b>active</b> Messages that the queue manager has opened for delivery. Only a limited number of messages is allowed to enter the <b>active</b> queue (leaky bucket strategy, for a fixed delivery rate). <b>deferred</b> Mail that could not be delivered upon the first attempt. The queue manager implements exponential backoff by doubling the time between delivery attempts. <b>corrupt</b> Unreadable or damaged queue files are moved here for inspection. <b>hold</b> Messages that are kept "on hold" are kept here until someone sets them free. <b>DELIVERY STATUS REPORTS</b> The <b>qmgr</b> daemon keeps an eye on per-message delivery sta- tus reports in the following directories. Each status report file has the same name as the corresponding message file: <b>bounce</b> Per-recipient status information about why mail is bounced. These files are maintained by the <a href="bounce.8.html"><b>bounce</b>(8)</a> daemon. <b>defer</b> Per-recipient status information about why mail is delayed. These files are maintained by the <a href="defer.8.html"><b>defer</b>(8)</a> daemon. <b>trace</b> Per-recipient status information as requested with the Postfix "<b>sendmail -v</b>" or "<b>sendmail -bv</b>" com- mand. These files are maintained by the <a href="trace.8.html"><b>trace</b>(8)</a> daemon. The <b>qmgr</b> daemon is responsible for asking the <a href="bounce.8.html"><b>bounce</b>(8)</a>, <a href="defer.8.html"><b>defer</b>(8)</a> or <a href="trace.8.html"><b>trace</b>(8)</a> daemons to send delivery reports. <b>STRATEGIES</b> The queue manager implements a variety of strategies for either opening queue files (input) or for message delivery (output). <b>leaky bucket</b> This strategy limits the number of messages in the <b>active</b> queue and prevents the queue manager from running out of memory under heavy load. <b>fairness</b> When the <b>active</b> queue has room, the queue manager takes one message from the <a href="QSHAPE_README.html#incoming_queue"><b>incoming</b> queue</a> and one from the <b>deferred</b> queue. This prevents a large mail backlog from blocking the delivery of new mail. <b>slow start</b> This strategy eliminates "thundering herd" problems by slowly adjusting the number of parallel deliver- ies to the same destination. <b>round robin</b> The queue manager sorts delivery requests by desti- nation. Round-robin selection prevents one desti- nation from dominating deliveries to other destina- tions. <b>exponential backoff</b> Mail that cannot be delivered upon the first attempt is deferred. The time interval between delivery attempts is doubled after each attempt. <b>destination status cache</b> The queue manager avoids unnecessary delivery attempts by maintaining a short-term, in-memory list of unreachable destinations. <b>preemptive message scheduling</b> The queue manager attempts to minimize the average per-recipient delay while still preserving the cor- rect per-message delays, using a sophisticated pre- emptive message scheduling. <b>TRIGGERS</b> On an idle system, the queue manager waits for the arrival of trigger events, or it waits for a timer to go off. A trigger is a one-byte message. Depending on the message received, the queue manager performs one of the following actions (the message is followed by the symbolic constant used internally by the software): <b>D (QMGR_REQ_SCAN_DEFERRED)</b> Start a <a href="QSHAPE_README.html#deferred_queue">deferred queue</a> scan. If a deferred queue scan is already in progress, that scan will be restarted as soon as it finishes. <b>I (QMGR_REQ_SCAN_INCOMING)</b> Start an <a href="QSHAPE_README.html#incoming_queue">incoming queue</a> scan. If an incoming queue scan is already in progress, that scan will be restarted as soon as it finishes. <b>A (QMGR_REQ_SCAN_ALL)</b> Ignore <a href="QSHAPE_README.html#deferred_queue">deferred queue</a> file time stamps. The request affects the next <a href="QSHAPE_README.html#deferred_queue">deferred queue</a> scan. <b>F (QMGR_REQ_FLUSH_DEAD)</b> Purge all information about dead transports and destinations. <b>W (TRIGGER_REQ_WAKEUP)</b> Wakeup call, This is used by the master server to instantiate servers that should not go away for- ever. The action is to start an <a href="QSHAPE_README.html#incoming_queue">incoming queue</a> scan. The <b>qmgr</b> daemon reads an entire buffer worth of triggers. Multiple identical trigger requests are collapsed into one, and trigger requests are sorted so that <b>A</b> and <b>F</b> pre- cede <b>D</b> and <b>I</b>. Thus, in order to force a <a href="QSHAPE_README.html#deferred_queue">deferred queue</a> run, one would request <b>A F D</b>; in order to notify the queue manager of the arrival of new mail one would request <b>I</b>. <b>STANDARDS</b> None. The <b>qmgr</b> daemon does not interact with the outside world. <b>SECURITY</b> The <b>qmgr</b> daemon is not security sensitive. It reads sin- gle-character messages from untrusted local users, and thus may be susceptible to denial of service attacks. The <b>qmgr</b> daemon does not talk to the outside world, and it can be run at fixed low privilege in a chrooted environment. <b>DIAGNOSTICS</b> Problems and transactions are logged to the syslog daemon. Corrupted message files are saved to the <b>corrupt</b> queue for further inspection. Depending on the setting of the <b><a href="postconf.5.html#notify_classes">notify_classes</a></b> parameter, the postmaster is notified of bounces and of other trou- ble. <b>BUGS</b> A single queue manager process has to compete for disk access with multiple front-end processes such as <b>smtpd</b>. A sudden burst of inbound mail can negatively impact out- bound delivery rates. <b>CONFIGURATION PARAMETERS</b> Changes to <b>main.cf</b> are not picked up automatically as <a href="qmgr.8.html">qmgr(8)</a> processes are persistent. Use the <b>postfix reload</b> command after a configuration change. The text below provides only a parameter summary. See <a href="postconf.5.html">postconf(5)</a> for more details including examples. In the text below, <i>transport</i> is the first field in a <b>mas-</b> <b>ter.cf</b> entry. <b>COMPATIBILITY CONTROLS</b> <b><a href="postconf.5.html#allow_min_user">allow_min_user</a> (no)</b> Allow a recipient address to have `-' as the first character. <b>ACTIVE QUEUE CONTROLS</b> <b><a href="postconf.5.html#qmgr_clog_warn_time">qmgr_clog_warn_time</a> (300s)</b> The minimal delay between warnings that a specific destination is clogging up the Postfix active queue. <b><a href="postconf.5.html#qmgr_message_active_limit">qmgr_message_active_limit</a> (20000)</b> The maximal number of messages in the <a href="QSHAPE_README.html#active_queue">active queue</a>. <b><a href="postconf.5.html#qmgr_message_recipient_limit">qmgr_message_recipient_limit</a> (20000)</b> 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" desti- nation status cache. <b><a href="postconf.5.html#qmgr_message_recipient_minimum">qmgr_message_recipient_minimum</a> (10)</b> The minimal number of in-memory recipients for any message. <b><a href="postconf.5.html#default_recipient_limit">default_recipient_limit</a> (10000)</b> The default per-transport upper limit on the number of in-memory recipients. <i>transport</i><b>_recipient_limit ($<a href="postconf.5.html#default_recipient_limit">default_recipient_limit</a>)</b> Idem, for delivery via the named message <i>transport</i>. <b><a href="postconf.5.html#default_extra_recipient_limit">default_extra_recipient_limit</a> (1000)</b> The default value for the extra per-transport limit imposed on the number of in-memory recipients. <i>transport</i><b>_extra_recipient_limit ($default_extra_recipi-</b> <b>ent_limit)</b> Idem, for delivery via the named message <i>transport</i>. <b>DELIVERY CONCURRENCY CONTROLS</b> <b><a href="postconf.5.html#initial_destination_concurrency">initial_destination_concurrency</a> (5)</b> The initial per-destination concurrency level for parallel delivery to the same destination. <b><a href="postconf.5.html#default_destination_concurrency_limit">default_destination_concurrency_limit</a> (20)</b> The default maximal number of parallel deliveries to the same destination. <i>transport</i><b>_destination_concurrency_limit ($<a href="postconf.5.html#default_destination_concurrency_limit">default_destina</a>-</b> <b><a href="postconf.5.html#default_destination_concurrency_limit">tion_concurrency_limit</a>)</b> Idem, for delivery via the named message <i>transport</i>. <b>RECIPIENT SCHEDULING CONTROLS</b> <b><a href="postconf.5.html#default_destination_recipient_limit">default_destination_recipient_limit</a> (50)</b> The default maximal number of recipients per mes- sage delivery. <i>transport</i><b>_destination_recipient_limit ($<a href="postconf.5.html#default_destination_recipient_limit">default_destina</a>-</b> <b><a href="postconf.5.html#default_destination_recipient_limit">tion_recipient_limit</a>)</b> Idem, for delivery via the named message <i>transport</i>. <b>MESSAGE SCHEDULING CONTROLS</b> <b><a href="postconf.5.html#default_delivery_slot_cost">default_delivery_slot_cost</a> (5)</b> How often the Postfix queue manager's scheduler is allowed to preempt delivery of one message with another. <i>transport</i><b>_delivery_slot_cost ($<a href="postconf.5.html#default_delivery_slot_cost">default_delivery_slot_cost</a>)</b> Idem, for delivery via the named message <i>transport</i>. <b><a href="postconf.5.html#default_minimum_delivery_slots">default_minimum_delivery_slots</a> (3)</b> How many recipients a message must have in order to invoke the Postfix queue manager's scheduling algo- rithm at all. <i>transport</i><b>_minimum_delivery_slots ($<a href="postconf.5.html#default_minimum_delivery_slots">default_minimum_deliv</a>-</b> <b><a href="postconf.5.html#default_minimum_delivery_slots">ery_slots</a>)</b> Idem, for delivery via the named message <i>transport</i>. <b><a href="postconf.5.html#default_delivery_slot_discount">default_delivery_slot_discount</a> (50)</b> The default value for transport-specific _deliv- ery_slot_discount settings. <i>transport</i><b>_delivery_slot_discount ($<a href="postconf.5.html#default_delivery_slot_discount">default_deliv</a>-</b> <b><a href="postconf.5.html#default_delivery_slot_discount">ery_slot_discount</a>)</b> Idem, for delivery via the named message <i>transport</i>. <b><a href="postconf.5.html#default_delivery_slot_loan">default_delivery_slot_loan</a> (3)</b> The default value for transport-specific _deliv- ery_slot_loan settings. <i>transport</i><b>_delivery_slot_loan ($<a href="postconf.5.html#default_delivery_slot_loan">default_delivery_slot_loan</a>)</b> Idem, for delivery via the named message <i>transport</i>. <b>OTHER RESOURCE AND RATE CONTROLS</b> <b><a href="postconf.5.html#minimal_backoff_time">minimal_backoff_time</a> (1000s)</b> The minimal time between attempts to deliver a deferred message. <b><a href="postconf.5.html#maximal_backoff_time">maximal_backoff_time</a> (4000s)</b> The maximal time between attempts to deliver a deferred message. <b><a href="postconf.5.html#maximal_queue_lifetime">maximal_queue_lifetime</a> (5d)</b> The maximal time a message is queued before it is sent back as undeliverable. <b><a href="postconf.5.html#queue_run_delay">queue_run_delay</a> (1000s)</b> The time between <a href="QSHAPE_README.html#deferred_queue">deferred queue</a> scans by the queue manager. <b><a href="postconf.5.html#transport_retry_time">transport_retry_time</a> (60s)</b> The time between attempts by the Postfix queue man- ager to contact a malfunctioning message delivery transport. Available in Postfix version 2.1 and later: <b><a href="postconf.5.html#bounce_queue_lifetime">bounce_queue_lifetime</a> (5d)</b> The maximal time a bounce message is queued before it is considered undeliverable. <b>MISCELLANEOUS CONTROLS</b> <b><a href="postconf.5.html#config_directory">config_directory</a> (see 'postconf -d' output)</b> The default location of the Postfix main.cf and master.cf configuration files. <b><a href="postconf.5.html#daemon_timeout">daemon_timeout</a> (18000s)</b> How much time a Postfix daemon process may take to handle a request before it is terminated by a built-in watchdog timer. <b><a href="postconf.5.html#defer_transports">defer_transports</a> (empty)</b> The names of message delivery transports that should not be delivered to unless someone issues "<b>sendmail -q</b>" or equivalent. <b><a href="postconf.5.html#helpful_warnings">helpful_warnings</a> (yes)</b> Log warnings about problematic configuration set- tings, and provide helpful suggestions. <b><a href="postconf.5.html#ipc_timeout">ipc_timeout</a> (3600s)</b> The time limit for sending or receiving information over an internal communication channel. <b><a href="postconf.5.html#process_id">process_id</a> (read-only)</b> The process ID of a Postfix command or daemon pro- cess. <b><a href="postconf.5.html#process_name">process_name</a> (read-only)</b> The process name of a Postfix command or daemon process. <b><a href="postconf.5.html#queue_directory">queue_directory</a> (see 'postconf -d' output)</b> The location of the Postfix top-level queue direc- tory. <b><a href="postconf.5.html#syslog_facility">syslog_facility</a> (mail)</b> The syslog facility of Postfix logging. <b><a href="postconf.5.html#syslog_name">syslog_name</a> (postfix)</b> The mail system name that is prepended to the pro- cess name in syslog records, so that "smtpd" becomes, for example, "postfix/smtpd". <b>FILES</b> /var/spool/postfix/incoming, <a href="QSHAPE_README.html#incoming_queue">incoming queue</a> /var/spool/postfix/active, <a href="QSHAPE_README.html#active_queue">active queue</a> /var/spool/postfix/deferred, <a href="QSHAPE_README.html#deferred_queue">deferred queue</a> /var/spool/postfix/bounce, non-delivery status /var/spool/postfix/defer, non-delivery status /var/spool/postfix/trace, delivery status <b>SEE ALSO</b> <a href="trivial-rewrite.8.html">trivial-rewrite(8)</a>, address routing <a href="bounce.8.html">bounce(8)</a>, delivery status reports <a href="postconf.5.html">postconf(5)</a>, configuration parameters <a href="master.8.html">master(8)</a>, process manager syslogd(8) system logging <b>README FILES</b> <a href="SCHEDULER_README.html">SCHEDULER_README</a>, scheduling algorithm <a href="QSHAPE_README.html">QSHAPE_README</a>, Postfix queue analysis <b>LICENSE</b> The Secure Mailer license must be distributed with this software. <b>AUTHOR(S)</b> Wietse Venema IBM T.J. Watson Research P.O. Box 704 Yorktown Heights, NY 10598, USA Scheduler enhancements: Patrik Rak Modra 6 155 00, Prague, Czech Republic QMGR(8) </pre> </body> </html>