oqmgr



OQMGR(8)                                                              OQMGR(8)




NAME

       oqmgr - old Postfix queue manager


SYNOPSIS

       oqmgr [generic Postfix daemon options]


DESCRIPTION

       The  oqmgr(8)  daemon  awaits the arrival of incoming mail and arranges
       for its delivery via Postfix delivery processes.  The actual mail rout-
       ing  strategy is delegated to the trivial-rewrite(8) daemon.  This pro-
       gram 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 oqmgr(8) daemon maintains the following queues:

       incoming
              Inbound mail from the network, or mail picked up  by  the  local
              pickup(8) agent 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 oqmgr(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  oqmgr(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.


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 oqmgr(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

       None. The oqmgr(8) daemon does not interact with the outside world.


SECURITY

       The  oqmgr(8) daemon is not security sensitive. It reads single-charac-
       ter messages from untrusted local users, and thus may be susceptible to
       denial  of  service  attacks.  The oqmgr(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(8) daemon.  Cor-
       rupted message files are saved to the corrupt queue for further inspec-
       tion.

       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  oqmgr(8)  is  a
       persistent process. Use the command "postfix reload" after a configura-
       tion 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

       allow_min_user (no)
              Allow a recipient address to have ‘-’ as the first character.


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.


DELIVERY CONCURRENCY CONTROLS

       qmgr_fudge_factor (100)
              Obsolete feature: the percentage of delivery  resources  that  a
              busy  mail  system  will  use up for delivery of a large mailing
              list message.

       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
              Idem, for delivery via the named message transport.


RECIPIENT SCHEDULING CONTROLS

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

       transport_destination_recipient_limit
              Idem, for delivery via the named message transport.


OTHER RESOURCE AND RATE CONTROLS

       minimal_backoff_time (1000s)
              The minimal time between attempts to deliver a deferred message.

       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 (1000s)
              The time between deferred queue scans by the queue manager.

       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)
              The maximal time a bounce message is queued before it is consid-
              ered undeliverable.


MISCELLANEOUS CONTROLS

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

       daemon_timeout (18000s)
              How much time a Postfix daemon process  may  take  to  handle  a
              request before it is terminated by a built-in watchdog timer.

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

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

       ipc_timeout (3600s)
              The time limit for sending  or  receiving  information  over  an
              internal communication channel.

       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 (postfix)
              The  mail  system  name that is prepended to the process name in
              syslog records, so that "smtpd"  becomes,  for  example,  "post-
              fix/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.
       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



                                                                      OQMGR(8)

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