OQMGR(8) OQMGR(8)
NAME
oqmgr - old Postfix queue manager
SYNOPSIS
oqmgr [generic Postfix daemon options]
DESCRIPTION
The oqmgr 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 triv-
ial-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 daemon maintains the following queues:
incoming
Inbound mail from the network, or mail picked up by
the local pickup 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 daemon keeps an eye on per-message delivery sta-
tus 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 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 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 pre-
cede 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 daemon does not interact with the outside
world.
SECURITY
The oqmgr daemon is not security sensitive. It reads sin-
gle-character messages from untrusted local users, and
thus may be susceptible to denial of service attacks. The
oqmgr 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 daemon.
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 smtpd. A
sudden burst of inbound mail can negatively impact out-
bound delivery rates.
CONFIGURATION PARAMETERS
Changes to main.cf are not picked up automatically, as
oqmgr(8) processes are persistent. Use the command "post-
fix 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 pro-
cess.
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 pro-
cess 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(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)