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OQMGR(8)                    System Manager's Manual                   OQMGR(8)

       oqmgr - old Postfix queue manager

       oqmgr [generic Postfix daemon options]

       The oqmgr(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

       The oqmgr(8) daemon maintains the following queues:

              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).

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

              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.

       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
              maintained 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.

       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.

              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

       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

       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):

              Start a deferred queue scan.  If a deferred queue scan is
              already in progress, that scan will be restarted as soon as it

              Start an incoming queue scan. If an incoming queue scan is
              already in progress, that scan will be restarted as soon as it

              Ignore deferred queue file time stamps. The request affects the
              next deferred queue scan.

              Purge all information about dead transports and destinations.

              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.

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

       The oqmgr(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 oqmgr(8) daemon does not
       talk to the outside world, and it can be run at fixed low privilege in
       a chrooted environment.

       Problems and transactions are logged to the syslog(8) daemon.
       Corrupted message files are saved to the corrupt queue for further

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

       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.

       Changes to main.cf are not picked up automatically, as oqmgr(8) is a
       persistent process. Use the command "postfix reload" 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.

       Available before Postfix version 2.5:

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

       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.


       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_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

              Idem, for delivery via the named message transport.

       Available in Postfix version 2.5 and later:

              Initial concurrency for delivery via the named message

       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).

              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.

              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.

              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.


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

              Idem, for delivery via the named message transport.


       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

       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.


       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.


       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,

       /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

       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

       Use "postconf readme_directory" or "postconf html_directory" to locate
       this information.
       QSHAPE_README, Postfix queue analysis

       The Secure Mailer license must be distributed with this software.

       Wietse Venema
       IBM T.J. Watson Research
       P.O. Box 704
       Yorktown Heights, NY 10598, USA