Provided by: postfix_3.1.0-3_amd64 bug

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
              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 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
              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 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
              interval 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
       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 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
       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 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
       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_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
              specific destination is considered unavailable (and further delivery is suspended).

       transport_destination_concurrency_failed_cohort_limit
       ($default_destination_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 handshake failure.

       transport_destination_concurrency_negative_feedback
       ($default_destination_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 handshake failure.

       transport_destination_concurrency_positive_feedback
       ($default_destination_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 performance 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_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
              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 maximal_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 contact 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 recipient 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 information 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 configuration 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 logging sub-second  delay
              values.

       helpful_warnings (yes)
              Log   warnings  about  problematic  configuration  settings,  and  provide  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)
              The mail system name that is prepended to the process name in  syslog  records,  so
              that "smtpd" becomes, for example, "postfix/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

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

                                                                                   QMGR(8postfix)