OQMGR
Section: Maintenance Commands (8)
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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 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 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 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-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 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
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_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 ($default_destination_concurrency_negative_feedback)
-
Idem, for delivery via the named message transport.
- default_destination_concurrency_positive_feedback (1)
-
The per-destination amount of delivery concurrency positive
feedback, after a delivery completes without connection or handshake
failure.
- transport_destination_concurrency_positive_feedback ($default_destination_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 performance
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
maximal_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 contact
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 recipient 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 information
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
configuration 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 logging
sub-second delay values.
- helpful_warnings (yes)
-
Log warnings about problematic configuration settings, and provide
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
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
Wietse Venema
Google, Inc.
111 8th Avenue
New York, NY 10011, USA
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- MAIL QUEUES
-
- DELIVERY STATUS REPORTS
-
- STRATEGIES
-
- TRIGGERS
-
- STANDARDS
-
- SECURITY
-
- DIAGNOSTICS
-
- BUGS
-
- CONFIGURATION PARAMETERS
-
- COMPATIBILITY CONTROLS
-
- ACTIVE QUEUE CONTROLS
-
- DELIVERY CONCURRENCY CONTROLS
-
- RECIPIENT SCHEDULING CONTROLS
-
- OTHER RESOURCE AND RATE CONTROLS
-
- SAFETY CONTROLS
-
- MISCELLANEOUS CONTROLS
-
- FILES
-
- SEE ALSO
-
- README FILES
-
- LICENSE
-
- AUTHOR(S)
-
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