OQMGR(8) System Manager's Manual 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 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 back‐
off 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 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.
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 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 col‐
lapsed 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-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.
DIAGNOSTICS
Problems and transactions are logged to the syslog(8) daemon. Corrupted message files are saved to the cor‐
rupt queue for further inspection.
Depending on the setting of the notify_classes parameter, the postmaster is notified of bounces and of other
trouble.
BUGS
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 $default_fil‐
ter_nexthop instead; when that value is empty, use the domain in the recipient address.
ACTIVE QUEUE CONTROLS
qmgr_clog_warn_time (300s)
The minimal delay between warnings that a specific destination is clogging up the Postfix active queue.
qmgr_message_active_limit (20000)
The maximal number of messages in the active queue.
qmgr_message_recipient_limit (20000)
The maximal number of recipients held in memory by the Postfix queue manager, and the maximal size of
the short-term, in-memory "dead" destination status cache.
DELIVERY CONCURRENCY CONTROLS
qmgr_fudge_factor (100)
Obsolete feature: the percentage of delivery resources that a busy mail system will use up for delivery
of a large mailing list message.
initial_destination_concurrency (5)
The initial per-destination concurrency level for parallel delivery to the same destination.
default_destination_concurrency_limit (20)
The default maximal number of parallel deliveries to the same destination.
transport_destination_concurrency_limit ($default_destination_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_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)
The maximal time a message is queued before it is sent back as undeliverable.
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; 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.
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.
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
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".
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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