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 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 mail-drop maildrop
drop 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 exponen-tial exponential
tial 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 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
deliveries to the same destination.
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 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 inter-nally internally
nally 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-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 corrupt queue for further inspection.
Depending on the setting of the notify_classes parameter, the postmaster is notified of bounces and
of other trouble.
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 com-mand command
mand "postfix reload" after a configuration change.
The text below provides only a parameter summary. See postconf(5) for more details including exam-ples. examples.
ples.
In the text below, transport is the first field in a master.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" 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
Idem, for delivery via the named message transport.
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 (version dependent)
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 (version dependent)
The time between deferred queue scans by the queue manager.
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.
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 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.
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 directory.
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
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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