# man > OQMGR(8postfix) [OQMGR(8postfix)](https://www.chedong.com/phpMan.php/man/OQMGR/8postfix/markdown) [OQMGR(8postfix)](https://www.chedong.com/phpMan.php/man/OQMGR/8postfix/markdown) ## NAME oqmgr - old Postfix queue manager ## SYNOPSIS **oqmgr** [generic Postfix daemon options] ## DESCRIPTION The [**oqmgr**(8)](https://www.chedong.com/phpMan.php/man/oqmgr/8/markdown) 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-re**‐‐ [**write**(8)](https://www.chedong.com/phpMan.php/man/write/8/markdown) daemon. This program expects to be run from the [**master**(8)](https://www.chedong.com/phpMan.php/man/master/8/markdown) process manager. Mail addressed to the local **double-bounce** address is logged and discarded. This stops poten‐ tial loops caused by undeliverable bounce notifications. ## MAIL QUEUES The [**oqmgr**(8)](https://www.chedong.com/phpMan.php/man/oqmgr/8/markdown) daemon maintains the following queues: ### incoming Inbound mail from the network, or mail picked up by the local [**pickup**(8)](https://www.chedong.com/phpMan.php/man/pickup/8/markdown) agent from the **maildrop** directory. **active** Messages that the queue manager has opened for delivery. Only a limited number of mes‐ sages is allowed to enter the **active** queue (leaky bucket strategy, for a fixed deliv‐ ery 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)](https://www.chedong.com/phpMan.php/man/oqmgr/8/markdown) daemon keeps an eye on per-message delivery status reports in the following di‐ rectories. 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 main‐ tained by the [**bounce**(8)](https://www.chedong.com/phpMan.php/man/bounce/8/markdown) daemon. **defer** Per-recipient status information about why mail is delayed. These files are main‐ tained by the [**defer**(8)](https://www.chedong.com/phpMan.php/man/defer/8/markdown) daemon. **trace** Per-recipient status information as requested with the Postfix "**sendmail** **-v**" or "**send**‐‐ **mail** **-bv**" command. These files are maintained by the [**trace**(8)](https://www.chedong.com/phpMan.php/man/trace/8/markdown) daemon. The [**oqmgr**(8)](https://www.chedong.com/phpMan.php/man/oqmgr/8/markdown) daemon is responsible for asking the [**bounce**(8)](https://www.chedong.com/phpMan.php/man/bounce/8/markdown), [**defer**(8)](https://www.chedong.com/phpMan.php/man/defer/8/markdown) or [**trace**(8)](https://www.chedong.com/phpMan.php/man/trace/8/markdown) 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 block‐ ing 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 pre‐ vents 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)](https://www.chedong.com/phpMan.php/man/oqmgr/8/markdown) daemon reads an entire buffer worth of triggers. Multiple identical trigger re‐ quests 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)](https://www.chedong.com/phpMan.php/man/oqmgr/8/markdown) daemon is not security sensitive. It reads single-character messages from un‐ trusted local users, and thus may be susceptible to denial of service attacks. The [**oqmgr**(8)](https://www.chedong.com/phpMan.php/man/oqmgr/8/markdown) daemon does not talk to the outside world, and it can be run at fixed low privilege in a ch‐ rooted environment. ## DIAGNOSTICS Problems and transactions are logged to the [**syslogd**(8)](https://www.chedong.com/phpMan.php/man/syslogd/8/markdown) or [**postlogd**(8)](https://www.chedong.com/phpMan.php/man/postlogd/8/markdown) daemon. Corrupted mes‐ sage 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 pro‐ cesses such as [**cleanup**(8)](https://www.chedong.com/phpMan.php/man/cleanup/8/markdown). A sudden burst of inbound mail can negatively impact outbound de‐ livery rates. ## CONFIGURATION PARAMETERS Changes to **main.cf** are not picked up automatically, as [**oqmgr**(8)](https://www.chedong.com/phpMan.php/man/oqmgr/8/markdown) is a persistent process. Use the command "**postfix** **reload**" after a configuration change. The text below provides only a parameter summary. See [**postconf**(5)](https://www.chedong.com/phpMan.php/man/postconf/5/markdown) 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 $default_filter_nexthop instead; when that value is empty, use the domain in the recipient address. ## ACTIVE QUEUE CONTROLS **qmgr**___**clog**___**warn**___**time** **(300s)** The minimal delay between warnings that a specific destination is clogging up the Postfix active queue. **qmgr**___**message**___**active**___**limit** **(20000)** The maximal number of messages in the active queue. **qmgr**___**message**___**recipient**___**limit** **(20000)** The maximal number of recipients held in memory by the Postfix queue manager, and the maximal size of the short-term, in-memory "dead" destination status cache. ## DELIVERY CONCURRENCY CONTROLS **qmgr**___**fudge**___**factor** **(100)** Obsolete feature: the percentage of delivery resources that a busy mail system will use up for delivery of a large mailing list message. **initial**___**destination**___**concurrency** **(5)** The initial per-destination concurrency level for parallel delivery to the same desti‐ nation. **default**___**destination**___**concurrency**___**limit** **(20)** The default maximal number of parallel deliveries to the same destination. **transport**___**destination**___**concurrency**___**limit** **($default**___**destination**___**concurrency**___**limit)** A transport-specific override for the default_destination_concurrency_limit parameter value, where _transport_ is the master.cf name of the message delivery transport. Available in Postfix version 2.5 and later: **transport**___**initial**___**destination**___**concurrency** **($initial**___**destination**___**concurrency)** A transport-specific override for the initial_destination_concurrency parameter value, where _transport_ is the master.cf name of the message delivery transport. **default**___**destination**___**concurrency**___**failed**___**cohort**___**limit** **(1)** How many pseudo-cohorts must suffer connection or handshake failure before a specific destination is considered unavailable (and further delivery is suspended). **transport**___**destination**___**concurrency**___**failed**___**cohort**___**limit** **($default**___**destination**___**concur**‐‐ **rency**___**failed**___**cohort**___**limit)** A transport-specific override for the default_destination_concurrency_failed_co‐ hort_limit parameter value, where _transport_ is the master.cf name of the message de‐ livery 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** **($default**___**destination**___**concurrency**___**nega**‐‐ **tive**___**feedback)** A transport-specific override for the default_destination_concurrency_negative_feed‐ back parameter value, where _transport_ is the master.cf name of the message delivery transport. **default**___**destination**___**concurrency**___**positive**___**feedback** **(1)** The per-destination amount of delivery concurrency positive feedback, after a delivery completes without connection or handshake failure. **transport**___**destination**___**concurrency**___**positive**___**feedback** **($default**___**destination**___**concurrency**___**posi**‐‐ **tive**___**feedback)** A transport-specific override for the default_destination_concurrency_positive_feed‐ back parameter value, where _transport_ is the master.cf name of the message delivery 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** **($default**___**destination**___**recipient**___**limit)** A transport-specific override for the default_destination_recipient_limit parameter value, where _transport_ is the master.cf name of the message delivery transport. ## OTHER RESOURCE AND RATE CONTROLS **minimal**___**backoff**___**time** **(300s)** The minimal time between attempts to deliver a deferred message; prior to Postfix 2.4 the default value was 1000s. **maximal**___**backoff**___**time** **(4000s)** The maximal time between attempts to deliver a deferred message. **maximal**___**queue**___**lifetime** **(5d)** Consider a message as undeliverable, when delivery fails with a temporary error, and the time in the queue has reached the maximal_queue_lifetime limit. **queue**___**run**___**delay** **(300s)** The time between deferred queue scans by the queue manager; prior to Postfix 2.4 the default value was 1000s. **transport**___**retry**___**time** **(60s)** The time between attempts by the Postfix queue manager to contact a malfunctioning message delivery transport. Available in Postfix version 2.1 and later: **bounce**___**queue**___**lifetime** **(5d)** Consider a bounce message as undeliverable, when delivery fails with a temporary er‐ ror, and the time in the queue has reached the bounce_queue_lifetime limit. Available in Postfix version 2.5 and later: **default**___**destination**___**rate**___**delay** **(0s)** The default amount of delay that is inserted between individual message deliveries to the same destination and over the same message delivery transport. **transport**___**destination**___**rate**___**delay** **($default**___**destination**___**rate**___**delay)** A transport-specific override for the default_destination_rate_delay parameter value, where _transport_ is the master.cf name of the message delivery transport. Available in Postfix version 3.1 and later: **default**___**transport**___**rate**___**delay** **(0s)** The default amount of delay that is inserted between individual message deliveries over the same message delivery transport, regardless of destination. **transport**___**transport**___**rate**___**delay** **($default**___**transport**___**rate**___**delay)** A transport-specific override for the default_transport_rate_delay parameter value, where the initial _transport_ in the parameter name is the master.cf name of the message delivery 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 Post‐ fix 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 sugges‐ tions. **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 exam‐ ple, "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 de‐ lay clears up. Available in Postfix 3.3 and later: **service**___**name** **(read-only)** The master.cf service name of a Postfix daemon process. Available in Postfix 3.5 and later: **info**___**log**___**address**___**format** **(external)** The email address form that will be used in non-debug logging (info, warning, etc.). ## 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)](https://www.chedong.com/phpMan.php/man/trivial-rewrite/8/markdown), address routing [bounce(8)](https://www.chedong.com/phpMan.php/man/bounce/8/markdown), delivery status reports [postconf(5)](https://www.chedong.com/phpMan.php/man/postconf/5/markdown), configuration parameters [master(5)](https://www.chedong.com/phpMan.php/man/master/5/markdown), generic daemon options [master(8)](https://www.chedong.com/phpMan.php/man/master/8/markdown), process manager [postlogd(8)](https://www.chedong.com/phpMan.php/man/postlogd/8/markdown), Postfix logging [syslogd(8)](https://www.chedong.com/phpMan.php/man/syslogd/8/markdown), 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 [OQMGR(8postfix)](https://www.chedong.com/phpMan.php/man/OQMGR/8postfix/markdown)