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man pages section 8: System Administration Commands

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Updated: Thursday, June 13, 2019
 
 

qmgr (8)

Name

qmgr - Postfix queue manager

Synopsis

qmgr [generic Postfix daemon options]

Description

QMGR(8)                     System Manager's Manual                    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  dis-
       carded.   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 implements 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 maintained by the bounce(8) daemon.

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

       trace  Per-recipient status information as requested with  the  Postfix
              "sendmail  -v" or "sendmail -bv" command.  These files are main-
              tained 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 mes-
              sage  from  the  incoming 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 destina-
              tion.

       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 interval between delivery attempts  is  dou-
              bled after each attempt.

       destination status cache
              The  queue manager avoids unnecessary delivery attempts by main-
              taining a short-term, in-memory  list  of  unreachable  destina-
              tions.

       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 mes-
       sage.   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 out-
       side  world,  and  it  can  be run at fixed low privilege 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 postmas-
       ter is notified of bounces and of other trouble.

BUGS
       A single queue manager process has to compete for disk access with mul-
       tiple front-end processes 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 per-
       sistent process. Use the "postfix reload" command after a configuration
       change.

       The text below provides only a parameter summary. See  postconf(5)  for
       more details including 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 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_concur-
       rency_limit)
              Idem, for delivery via the named message transport.

       Available in Postfix version 2.5 and later:

       transport_initial_destination_concurrency ($initial_destination_concur-
       rency)
              Initial  concurrency  for  delivery via the named message trans-
              port.

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

       transport_destination_concurrency_failed_cohort_limit  ($default_desti-
       nation_concurrency_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  hand-
              shake failure.

       transport_destination_concurrency_negative_feedback  ($default_destina-
       tion_concurrency_negative_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 hand-
              shake failure.

       transport_destination_concurrency_positive_feedback  ($default_destina-
       tion_concurrency_positive_feedback)
              Idem, for delivery via the named message transport.

       destination_concurrency_feedback_debug (no)
              Make  the queue manager's feedback algorithm verbose for perfor-
              mance analysis purposes.

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

       transport_destination_recipient_limit     ($default_destination_recipi-
       ent_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 manager'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)
              Consider a message as undeliverable, when delivery fails with  a
              temporary error, and the time in the queue has reached the maxi-
              mal_queue_lifetime limit.

       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 con-
              tact a malfunctioning message delivery transport.

       Available in Postfix version 2.1 and later:

       bounce_queue_lifetime (5d)
              Consider a bounce message as undeliverable, when delivery  fails
              with  a  temporary  error, and the time in the queue has reached
              the bounce_queue_lifetime limit.

       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;  the  resulting behavior
              depends on the value of the corresponding per-destination recip-
              ient limit.

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

       Available in Postfix version 3.1 and later:

       default_transport_rate_delay (0s)
              The  default amount of delay that is inserted between individual
              deliveries over the same message delivery transport,  regardless
              of destination.

       transport_transport_rate_delay $default_transport_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 informa-
              tion over an internal communication channel.

       Available in Postfix version 3.1 and later:

       address_verify_pending_request_limit (see 'postconf -d' output)
              A  safety limit that prevents address verification requests from
              overwhelming the Postfix queue.

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

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

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

       helpful_warnings (yes)
              Log  warnings about problematic configuration settings, and pro-
              vide helpful suggestions.

       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)
              A prefix that  is  prepended  to  the  process  name  in  syslog
              records, so that, for example, "smtpd" becomes "prefix/smtpd".

       Available in Postfix version 3.0 and later:

       confirm_delay_cleared (no)
              After  sending  a "your message is delayed" notification, inform
              the sender when the delay clears up.

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


ATTRIBUTES
       See attributes(7) for descriptions of the following attributes:


       +---------------+------------------------------+
       |ATTRIBUTE TYPE |       ATTRIBUTE VALUE        |
       +---------------+------------------------------+
       |Availability   | service/network/smtp/postfix |
       +---------------+------------------------------+
       |Stability      | Volatile                     |
       +---------------+------------------------------+
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

       Wietse Venema
       Google, Inc.
       111 8th Avenue
       New York, NY 10011, USA



NOTES
       This software was built from source available at
       https://github.com/oracle/solaris-userland.  The original community
       source was downloaded from  https://archive.mgm51.com/mirrors/postfix-
       source/official/postfix-3.2.2.tar.gz

       Further information about this software can be found on the open source
       community website at http://www.postfix.org.



                                                                       QMGR(8)