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NetBSD 6.1.5 - man page for qmgr (netbsd section 8)

QMGR(8) 										  QMGR(8)

NAME
       qmgr - Postfix queue manager

SYNOPSIS
       qmgr [generic Postfix daemon options]

DESCRIPTION
       The  qmgr(8)  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 trivial-
       rewrite(8) daemon.  This program expects to be run from the master(8) process manager.

       Mail  addressed	to  the  local double-bounce address is logged and discarded.  This stops
       potential loops caused by undeliverable bounce notifications.

MAIL QUEUES
       The qmgr(8) daemon maintains the following queues:

       incoming
	      Inbound mail from the network, or mail picked up by the local pickup(8) daemon from
	      the maildrop directory.

       active Messages	that  the queue manager has opened for delivery. Only a limited number of
	      messages is allowed to enter the active queue (leaky bucket strategy, for  a  fixed
	      delivery rate).

       deferred
	      Mail  that  could not be delivered upon the first attempt. The queue manager imple-
	      ments exponential backoff by doubling the time between delivery attempts.

       corrupt
	      Unreadable or damaged queue files are moved here for inspection.

       hold   Messages that are kept "on hold" are kept here until someone sets them free.

DELIVERY STATUS REPORTS
       The qmgr(8) daemon keeps an eye on per-message delivery status reports  in  the	following
       directories. Each status report file has the same name as the corresponding message file:

       bounce Per-recipient  status information about why mail is bounced.  These files are main-
	      tained by the bounce(8) daemon.

       defer  Per-recipient status information about why mail is delayed.  These files are  main-
	      tained by the defer(8) daemon.

       trace  Per-recipient  status  information  as  requested with the Postfix "sendmail -v" or
	      "sendmail -bv" command.  These files are maintained by the trace(8) daemon.

       The qmgr(8) daemon is responsible for asking the bounce(8), defer(8) or	trace(8)  daemons
       to send delivery reports.

STRATEGIES
       The  queue  manager  implements	a  variety  of	strategies for either opening queue files
       (input) or for message delivery (output).

       leaky bucket
	      This strategy limits the number of messages in the active queue  and  prevents  the
	      queue manager from running out of memory under heavy load.

       fairness
	      When the active queue has room, the queue manager takes one message from the incom-
	      ing queue and one from the deferred queue. This prevents a large mail backlog  from
	      blocking the delivery of new mail.

       slow start
	      This  strategy eliminates "thundering herd" problems by slowly adjusting the number
	      of parallel deliveries to the same destination.

       round robin
	      The queue manager sorts delivery requests by  destination.   Round-robin	selection
	      prevents one destination from dominating deliveries to other destinations.

       exponential backoff
	      Mail  that cannot be delivered upon the first attempt is deferred.  The time inter-
	      val between delivery attempts is doubled after each attempt.

       destination status cache
	      The queue manager avoids unnecessary delivery attempts by maintaining a short-term,
	      in-memory list of unreachable destinations.

       preemptive message scheduling
	      The  queue manager attempts to minimize the average per-recipient delay while still
	      preserving the correct per-message delays, using a sophisticated preemptive message
	      scheduling.

TRIGGERS
       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):

       D (QMGR_REQ_SCAN_DEFERRED)
	      Start a deferred queue scan.  If a deferred queue scan is already in progress, that
	      scan will be restarted as soon as it finishes.

       I (QMGR_REQ_SCAN_INCOMING)
	      Start  an  incoming  queue  scan. If an incoming queue scan is already in progress,
	      that scan will be restarted as soon as it finishes.

       A (QMGR_REQ_SCAN_ALL)
	      Ignore deferred queue file time stamps. The request affects the next deferred queue
	      scan.

       F (QMGR_REQ_FLUSH_DEAD)
	      Purge all information about dead transports and destinations.

       W (TRIGGER_REQ_WAKEUP)
	      Wakeup  call,  This is used by the master server to instantiate servers that should
	      not go away forever. The action is to start an incoming queue scan.

       The qmgr(8) daemon reads an entire buffer worth of triggers.  Multiple  identical  trigger
       requests are collapsed into one, and trigger requests are sorted so that A and F precede D
       and I. Thus, in order to force a deferred queue run, one would request A F D; in order  to
       notify the queue manager of the arrival of new mail one would request I.

STANDARDS
       RFC 3463 (Enhanced status codes)
       RFC 3464 (Delivery status notifications)

SECURITY
       The  qmgr(8)  daemon  is  not  security sensitive. It reads single-character messages from
       untrusted local users, and thus may be susceptible  to  denial  of  service  attacks.  The
       qmgr(8)	daemon	does not talk to the outside world, and it can be run at fixed low privi-
       lege in a chrooted environment.

DIAGNOSTICS
       Problems and transactions are logged to the syslog daemon.  Corrupted  message  files  are
       saved to the corrupt queue for further inspection.

       Depending  on  the  setting of the notify_classes parameter, the postmaster is notified of
       bounces and of other trouble.

BUGS
       A single queue manager process has to compete for disk access with multiple front-end pro-
       cesses  such  as cleanup(8). A sudden burst of inbound mail can negatively impact outbound
       delivery rates.

CONFIGURATION PARAMETERS
       Changes to main.cf are not picked up automatically as qmgr(8) is a persistent process. Use
       the "postfix reload" command after a configuration change.

       The text below provides only a parameter summary. See postconf(5) for more details includ-
       ing examples.

       In the text below, transport is the first field in a master.cf entry.

COMPATIBILITY CONTROLS
       Available before Postfix version 2.5:

       allow_min_user (no)
	      Allow a sender or recipient address to have `-' as the first character.

       Available with Postfix version 2.7 and later:

       default_filter_nexthop (empty)
	      When a content_filter or FILTER request specifies no explicit next-hop destination,
	      use  $default_filter_nexthop  instead;  when that value is empty, use the domain in
	      the recipient address.

ACTIVE QUEUE CONTROLS
       qmgr_clog_warn_time (300s)
	      The minimal delay between warnings that a specific destination is clogging  up  the
	      Postfix active queue.

       qmgr_message_active_limit (20000)
	      The maximal number of messages in the active queue.

       qmgr_message_recipient_limit (20000)
	      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.

       qmgr_message_recipient_minimum (10)
	      The minimal number of in-memory recipients for any message.

       default_recipient_limit (20000)
	      The default per-transport upper limit on the number of in-memory recipients.

       transport_recipient_limit ($default_recipient_limit)
	      Idem, for delivery via the named message transport.

       default_extra_recipient_limit (1000)
	      The  default  value  for the extra per-transport limit imposed on the number of in-
	      memory recipients.

       transport_extra_recipient_limit ($default_extra_recipient_limit)
	      Idem, for delivery via the named message transport.

       Available in Postfix version 2.4 and later:

       default_recipient_refill_limit (100)
	      The default per-transport limit on the number of recipients refilled at once.

       transport_recipient_refill_limit ($default_recipient_refill_limit)
	      Idem, for delivery via the named message transport.

       default_recipient_refill_delay (5s)
	      The default per-transport maximum delay between recipients refills.

       transport_recipient_refill_delay ($default_recipient_refill_delay)
	      Idem, for delivery via the named message transport.

DELIVERY CONCURRENCY CONTROLS
       initial_destination_concurrency (5)
	      The initial per-destination concurrency level for parallel  delivery  to	the  same
	      destination.

       default_destination_concurrency_limit (20)
	      The default maximal number of parallel deliveries to the same destination.

       transport_destination_concurrency_limit ($default_destination_concurrency_limit)
	      Idem, for delivery via the named message transport.

       Available in Postfix version 2.5 and later:

       transport_initial_destination_concurrency ($initial_destination_concurrency)
	      Initial concurrency for delivery via the named message transport.

       default_destination_concurrency_failed_cohort_limit (1)
	      How  many  pseudo-cohorts must suffer connection or handshake failure before a spe-
	      cific destination is considered unavailable (and further delivery is suspended).

       transport_destination_concurrency_failed_cohort_limit	    ($default_destination_concur-
       rency_failed_cohort_limit)
	      Idem, for delivery via the named message transport.

       default_destination_concurrency_negative_feedback (1)
	      The  per-destination  amount  of	delivery  concurrency  negative feedback, after a
	      delivery completes with a connection or handshake failure.

       transport_destination_concurrency_negative_feedback ($default_destination_concurrency_neg-
       ative_feedback)
	      Idem, for delivery via the named message transport.

       default_destination_concurrency_positive_feedback (1)
	      The  per-destination  amount  of	delivery  concurrency  positive feedback, after a
	      delivery completes without connection or handshake failure.

       transport_destination_concurrency_positive_feedback ($default_destination_concurrency_pos-
       itive_feedback)
	      Idem, for delivery via the named message transport.

       destination_concurrency_feedback_debug (no)
	      Make  the  queue manager's feedback algorithm verbose for performance analysis pur-
	      poses.

RECIPIENT SCHEDULING CONTROLS
       default_destination_recipient_limit (50)
	      The default maximal number of recipients per message delivery.

       transport_destination_recipient_limit ($default_destination_recipient_limit)
	      Idem, for delivery via the named message transport.

MESSAGE SCHEDULING CONTROLS
       default_delivery_slot_cost (5)
	      How often the Postfix queue manager's scheduler is allowed to preempt  delivery  of
	      one message with another.

       transport_delivery_slot_cost ($default_delivery_slot_cost)
	      Idem, for delivery via the named message transport.

       default_minimum_delivery_slots (3)
	      How  many  recipients a message must have in order to invoke the Postfix queue man-
	      ager's scheduling algorithm at all.

       transport_minimum_delivery_slots ($default_minimum_delivery_slots)
	      Idem, for delivery via the named message transport.

       default_delivery_slot_discount (50)
	      The default value for transport-specific _delivery_slot_discount settings.

       transport_delivery_slot_discount ($default_delivery_slot_discount)
	      Idem, for delivery via the named message transport.

       default_delivery_slot_loan (3)
	      The default value for transport-specific _delivery_slot_loan settings.

       transport_delivery_slot_loan ($default_delivery_slot_loan)
	      Idem, for delivery via the named message transport.

OTHER RESOURCE AND RATE CONTROLS
       minimal_backoff_time (300s)
	      The minimal time between attempts to deliver a deferred message; prior  to  Postfix
	      2.4 the default value was 1000s.

       maximal_backoff_time (4000s)
	      The maximal time between attempts to deliver a deferred message.

       maximal_queue_lifetime (5d)
	      The maximal time a message is queued before it is sent back as undeliverable.

       queue_run_delay (300s)
	      The  time  between  deferred queue scans by the queue manager; prior to Postfix 2.4
	      the default value was 1000s.

       transport_retry_time (60s)
	      The time between attempts by the Postfix queue manager to contact a  malfunctioning
	      message delivery transport.

       Available in Postfix version 2.1 and later:

       bounce_queue_lifetime (5d)
	      The maximal time a bounce message is queued before it is considered undeliverable.

       Available in Postfix version 2.5 and later:

       default_destination_rate_delay (0s)
	      The  default  amount of delay that is inserted between individual deliveries to the
	      same destination; with per-destination recipient limit >	1,  a  destination  is	a
	      domain, otherwise it is a recipient.

       transport_destination_rate_delay $default_destination_rate_delay
	      Idem, for delivery via the named message transport.

SAFETY CONTROLS
       qmgr_daemon_timeout (1000s)
	      How  much  time a Postfix queue manager process may take to handle a request before
	      it is terminated by a built-in watchdog timer.

       qmgr_ipc_timeout (60s)
	      The time limit for the queue manager to send or receive information over an  inter-
	      nal communication channel.

MISCELLANEOUS CONTROLS
       config_directory (see 'postconf -d' output)
	      The default location of the Postfix main.cf and master.cf configuration files.

       defer_transports (empty)
	      The  names of message delivery transports that should not deliver mail unless some-
	      one issues "sendmail -q" or equivalent.

       delay_logging_resolution_limit (2)
	      The maximal number of digits after the decimal point when logging sub-second  delay
	      values.

       helpful_warnings (yes)
	      Log  warnings about problematic configuration settings, and provide helpful sugges-
	      tions.

       process_id (read-only)
	      The process ID of a Postfix command or daemon process.

       process_name (read-only)
	      The process name of a Postfix command or daemon process.

       queue_directory (see 'postconf -d' output)
	      The location of the Postfix top-level queue directory.

       syslog_facility (mail)
	      The syslog facility of Postfix logging.

       syslog_name (see 'postconf -d' output)
	      The mail system name that is prepended to the process name in  syslog  records,  so
	      that "smtpd" becomes, for example, "postfix/smtpd".

FILES
       /var/spool/postfix/incoming, incoming queue
       /var/spool/postfix/active, active queue
       /var/spool/postfix/deferred, deferred queue
       /var/spool/postfix/bounce, non-delivery status
       /var/spool/postfix/defer, non-delivery status
       /var/spool/postfix/trace, delivery status

SEE ALSO
       trivial-rewrite(8), address routing
       bounce(8), delivery status reports
       postconf(5), configuration parameters
       master(5), generic daemon options
       master(8), process manager
       syslogd(8), system logging

README FILES
       Use "postconf readme_directory" or "postconf html_directory" to locate this information.
       SCHEDULER_README, scheduling algorithm
       QSHAPE_README, Postfix queue analysis

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

       Preemptive scheduler enhancements:
       Patrik Rak
       Modra 6
       155 00, Prague, Czech Republic

											  QMGR(8)


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