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<title> Postfix manual - oqmgr(8) </title>
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oqmgr - old Postfix queue manager
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<b>oqmgr</b> [generic Postfix daemon options]
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The <b>oqmgr</b> daemon awaits the arrival of incoming mail and
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arranges for its delivery via Postfix delivery processes.
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The actual mail routing strategy is delegated to the <a href="trivial-rewrite.8.html"><b>triv-</b></a>
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<a href="trivial-rewrite.8.html"><b>ial-rewrite</b>(8)</a> daemon. This program expects to be run
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from the <a href="master.8.html"><b>master</b>(8)</a> process manager.
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Mail addressed to the local <b>double-bounce</b> address is
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logged and discarded. This stops potential loops caused
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by undeliverable bounce notifications.
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The <b>oqmgr</b> daemon maintains the following queues:
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Inbound mail from the network, or mail picked up by
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the local <b>pickup</b> agent from the <b>maildrop</b> directory.
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<b>active</b> Messages that the queue manager has opened for
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delivery. Only a limited number of messages is
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allowed to enter the <b>active</b> queue (leaky bucket
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strategy, for a fixed delivery rate).
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Mail that could not be delivered upon the first
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attempt. The queue manager implements exponential
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backoff by doubling the time between delivery
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Unreadable or damaged queue files are moved here
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<b>hold</b> Messages that are kept "on hold" are kept here
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until someone sets them free.
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<b>DELIVERY STATUS REPORTS</b>
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The <b>oqmgr</b> daemon keeps an eye on per-message delivery sta-
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tus reports in the following directories. Each status
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report file has the same name as the corresponding message
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<b>bounce</b> Per-recipient status information about why mail is
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bounced. These files are maintained by the
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<a href="bounce.8.html"><b>bounce</b>(8)</a> daemon.
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<b>defer</b> Per-recipient status information about why mail is
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delayed. These files are maintained by the
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<a href="defer.8.html"><b>defer</b>(8)</a> daemon.
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<b>trace</b> Per-recipient status information as requested with
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the Postfix "<b>sendmail -v</b>" or "<b>sendmail -bv</b>" com-
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mand. These files are maintained by the <a href="trace.8.html"><b>trace</b>(8)</a>
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The <b>oqmgr</b> daemon is responsible for asking the <a href="bounce.8.html"><b>bounce</b>(8)</a>,
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<a href="defer.8.html"><b>defer</b>(8)</a> or <a href="trace.8.html"><b>trace</b>(8)</a> daemons to send delivery reports.
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The queue manager implements a variety of strategies for
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either opening queue files (input) or for message delivery
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This strategy limits the number of messages in the
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<b>active</b> queue and prevents the queue manager from
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running out of memory under heavy load.
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When the <b>active</b> queue has room, the queue manager
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takes one message from the <a href="QSHAPE_README.html#incoming_queue"><b>incoming</b> queue</a> and one
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from the <b>deferred</b> queue. This prevents a large mail
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backlog from blocking the delivery of new mail.
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This strategy eliminates "thundering herd" problems
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by slowly adjusting the number of parallel deliver-
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ies to the same destination.
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The queue manager sorts delivery requests by desti-
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nation. Round-robin selection prevents one desti-
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nation from dominating deliveries to other destina-
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<b>exponential backoff</b>
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Mail that cannot be delivered upon the first
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attempt is deferred. The time interval between
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delivery attempts is doubled after each attempt.
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<b>destination status cache</b>
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The queue manager avoids unnecessary delivery
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attempts by maintaining a short-term, in-memory
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list of unreachable destinations.
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On an idle system, the queue manager waits for the arrival
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of trigger events, or it waits for a timer to go off. A
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trigger is a one-byte message. Depending on the message
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received, the queue manager performs one of the following
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actions (the message is followed by the symbolic constant
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used internally by the software):
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<b>D (QMGR_REQ_SCAN_DEFERRED)</b>
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Start a <a href="QSHAPE_README.html#deferred_queue">deferred queue</a> scan. If a deferred queue
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scan is already in progress, that scan will be
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restarted as soon as it finishes.
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<b>I (QMGR_REQ_SCAN_INCOMING)</b>
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Start an <a href="QSHAPE_README.html#incoming_queue">incoming queue</a> scan. If an incoming queue
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scan is already in progress, that scan will be
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restarted as soon as it finishes.
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<b>A (QMGR_REQ_SCAN_ALL)</b>
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Ignore <a href="QSHAPE_README.html#deferred_queue">deferred queue</a> file time stamps. The request
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affects the next <a href="QSHAPE_README.html#deferred_queue">deferred queue</a> scan.
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<b>F (QMGR_REQ_FLUSH_DEAD)</b>
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Purge all information about dead transports and
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<b>W (TRIGGER_REQ_WAKEUP)</b>
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Wakeup call, This is used by the master server to
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instantiate servers that should not go away for-
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ever. The action is to start an <a href="QSHAPE_README.html#incoming_queue">incoming queue</a>
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The <b>oqmgr</b> daemon reads an entire buffer worth of triggers.
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Multiple identical trigger requests are collapsed into
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one, and trigger requests are sorted so that <b>A</b> and <b>F</b> pre-
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cede <b>D</b> and <b>I</b>. Thus, in order to force a <a href="QSHAPE_README.html#deferred_queue">deferred queue</a>
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run, one would request <b>A F D</b>; in order to notify the queue
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manager of the arrival of new mail one would request <b>I</b>.
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None. The <b>oqmgr</b> daemon does not interact with the outside
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The <b>oqmgr</b> daemon is not security sensitive. It reads sin-
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gle-character messages from untrusted local users, and
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thus may be susceptible to denial of service attacks. The
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<b>oqmgr</b> daemon does not talk to the outside world, and it
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can be run at fixed low privilege in a chrooted environ-
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Problems and transactions are logged to the syslog daemon.
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Corrupted message files are saved to the <b>corrupt</b> queue for
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Depending on the setting of the <b><a href="postconf.5.html#notify_classes">notify_classes</a></b> parameter,
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the postmaster is notified of bounces and of other trou-
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A single queue manager process has to compete for disk
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access with multiple front-end processes such as <b>smtpd</b>. A
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sudden burst of inbound mail can negatively impact out-
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bound delivery rates.
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<b>CONFIGURATION PARAMETERS</b>
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Changes to <b>main.cf</b> are not picked up automatically, as
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<a href="qmgr.8.html">oqmgr(8)</a> processes are persistent. Use the command "<b>post-</b>
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<b>fix reload</b>" after a configuration change.
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The text below provides only a parameter summary. See
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<a href="postconf.5.html">postconf(5)</a> for more details including examples.
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In the text below, <i>transport</i> is the first field in a <b>mas-</b>
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<b>COMPATIBILITY CONTROLS</b>
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<b><a href="postconf.5.html#allow_min_user">allow_min_user</a> (no)</b>
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Allow a recipient address to have `-' as the first
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<b>ACTIVE QUEUE CONTROLS</b>
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<b><a href="postconf.5.html#qmgr_clog_warn_time">qmgr_clog_warn_time</a> (300s)</b>
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The minimal delay between warnings that a specific
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destination is clogging up the Postfix active
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<b><a href="postconf.5.html#qmgr_message_active_limit">qmgr_message_active_limit</a> (20000)</b>
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The maximal number of messages in the <a href="QSHAPE_README.html#active_queue">active queue</a>.
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<b><a href="postconf.5.html#qmgr_message_recipient_limit">qmgr_message_recipient_limit</a> (20000)</b>
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The maximal number of recipients held in memory by
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the Postfix queue manager, and the maximal size of
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the size of the short-term, in-memory "dead" desti-
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<b>DELIVERY CONCURRENCY CONTROLS</b>
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<b><a href="postconf.5.html#qmgr_fudge_factor">qmgr_fudge_factor</a> (100)</b>
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Obsolete feature: the percentage of delivery
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resources that a busy mail system will use up for
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delivery of a large mailing list message.
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<b><a href="postconf.5.html#initial_destination_concurrency">initial_destination_concurrency</a> (5)</b>
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The initial per-destination concurrency level for
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parallel delivery to the same destination.
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<b><a href="postconf.5.html#default_destination_concurrency_limit">default_destination_concurrency_limit</a> (20)</b>
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The default maximal number of parallel deliveries
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to the same destination.
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<i>transport</i><b>_destination_concurrency_limit</b>
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Idem, for delivery via the named message <i>transport</i>.
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<b>RECIPIENT SCHEDULING CONTROLS</b>
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<b><a href="postconf.5.html#default_destination_recipient_limit">default_destination_recipient_limit</a> (50)</b>
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The default maximal number of recipients per mes-
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<i>transport</i><b>_destination_recipient_limit</b>
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Idem, for delivery via the named message <i>transport</i>.
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<b>OTHER RESOURCE AND RATE CONTROLS</b>
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<b><a href="postconf.5.html#minimal_backoff_time">minimal_backoff_time</a> (1000s)</b>
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The minimal time between attempts to deliver a
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<b><a href="postconf.5.html#maximal_backoff_time">maximal_backoff_time</a> (4000s)</b>
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The maximal time between attempts to deliver a
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<b><a href="postconf.5.html#maximal_queue_lifetime">maximal_queue_lifetime</a> (5d)</b>
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The maximal time a message is queued before it is
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sent back as undeliverable.
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<b><a href="postconf.5.html#queue_run_delay">queue_run_delay</a> (1000s)</b>
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The time between <a href="QSHAPE_README.html#deferred_queue">deferred queue</a> scans by the queue
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<b><a href="postconf.5.html#transport_retry_time">transport_retry_time</a> (60s)</b>
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The time between attempts by the Postfix queue man-
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ager to contact a malfunctioning message delivery
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Available in Postfix version 2.1 and later:
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<b><a href="postconf.5.html#bounce_queue_lifetime">bounce_queue_lifetime</a> (5d)</b>
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The maximal time a bounce message is queued before
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it is considered undeliverable.
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<b>MISCELLANEOUS CONTROLS</b>
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<b><a href="postconf.5.html#config_directory">config_directory</a> (see 'postconf -d' output)</b>
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The default location of the Postfix main.cf and
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master.cf configuration files.
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<b><a href="postconf.5.html#daemon_timeout">daemon_timeout</a> (18000s)</b>
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How much time a Postfix daemon process may take to
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handle a request before it is terminated by a
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built-in watchdog timer.
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<b><a href="postconf.5.html#defer_transports">defer_transports</a> (empty)</b>
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The names of message delivery transports that
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should not be delivered to unless someone issues
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"<b>sendmail -q</b>" or equivalent.
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<b><a href="postconf.5.html#helpful_warnings">helpful_warnings</a> (yes)</b>
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Log warnings about problematic configuration set-
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tings, and provide helpful suggestions.
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<b><a href="postconf.5.html#ipc_timeout">ipc_timeout</a> (3600s)</b>
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The time limit for sending or receiving information
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over an internal communication channel.
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<b><a href="postconf.5.html#process_id">process_id</a> (read-only)</b>
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The process ID of a Postfix command or daemon pro-
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<b><a href="postconf.5.html#process_name">process_name</a> (read-only)</b>
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The process name of a Postfix command or daemon
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<b><a href="postconf.5.html#queue_directory">queue_directory</a> (see 'postconf -d' output)</b>
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The location of the Postfix top-level queue direc-
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<b><a href="postconf.5.html#syslog_facility">syslog_facility</a> (mail)</b>
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The syslog facility of Postfix logging.
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<b><a href="postconf.5.html#syslog_name">syslog_name</a> (postfix)</b>
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The mail system name that is prepended to the pro-
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cess name in syslog records, so that "smtpd"
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becomes, for example, "postfix/smtpd".
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/var/spool/postfix/incoming, <a href="QSHAPE_README.html#incoming_queue">incoming queue</a>
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/var/spool/postfix/active, <a href="QSHAPE_README.html#active_queue">active queue</a>
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/var/spool/postfix/deferred, <a href="QSHAPE_README.html#deferred_queue">deferred queue</a>
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/var/spool/postfix/bounce, non-delivery status
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/var/spool/postfix/defer, non-delivery status
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/var/spool/postfix/trace, delivery status
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<a href="trivial-rewrite.8.html">trivial-rewrite(8)</a>, address routing
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<a href="bounce.8.html">bounce(8)</a>, delivery status reports
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<a href="postconf.5.html">postconf(5)</a>, configuration parameters
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<a href="master.8.html">master(8)</a>, process manager
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syslogd(8) system logging
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<a href="QSHAPE_README.html">QSHAPE_README</a>, Postfix queue analysis
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The Secure Mailer license must be distributed with this
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IBM T.J. Watson Research
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Yorktown Heights, NY 10598, USA
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