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

    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
           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.

    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   ($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
                  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

    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
           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

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

                                                                          OQMGR(8)