    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  pro-
           cesses.   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 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  direc-
                  tory.

           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" com-
                  mand.  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.

    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 deliver-
                  ies to the same destination.

           round robin
                  The queue manager sorts delivery requests by desti-
                  nation.   Round-robin selection prevents one desti-
                  nation from dominating deliveries to other destina-
                  tions.

           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.

    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 for-
                  ever. The action is  to  start  an  incoming  queue
                  scan.

           The  oqmgr(8) daemon reads an entire buffer worth of trig-
           gers.  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  out-
           side world.

    SECURITY
           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 environ-
           ment.

    DIAGNOSTICS
           Problems and transactions are logged to the syslog(8) dae-
           mon.   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 trou-
           ble.

    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
           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  mas-
           ter.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" desti-
                  nation 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 mes-
                  sage 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 man-
                  ager 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.

    MISCELLANEOUS CONTROLS
           config_directory (see 'postconf -d' output)
                  The default location of  the  Postfix  main.cf  and
                  master.cf configuration 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 set-
                  tings, and provide 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 direc-
                  tory.

           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, "postfix/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
           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)