291 lines
13 KiB
HTML
291 lines
13 KiB
HTML
<html> <head> </head> <body> <pre>
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QMGR(8) QMGR(8)
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<b>NAME</b>
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qmgr - Postfix queue manager
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<b>SYNOPSIS</b>
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<b>qmgr</b> [generic Postfix daemon options]
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<b>DESCRIPTION</b>
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The <b>qmgr</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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silently discarded. This stops potential loops caused by
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undeliverable bounce notifications.
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Mail addressed to a user listed in the optional <b>relocated</b>
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database is bounced with a "user has moved to <i>new_loca-</i>
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<i>tion</i>" message. See <a href="relocated.5.html"><b>relocated</b>(5)</a> for a precise description.
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<b>MAIL</b> <b>QUEUES</b>
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The <b>qmgr</b> daemon maintains the following queues:
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<b>incoming</b>
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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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<b>deferred</b>
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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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attempts.
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<b>corrupt</b>
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Unreadable or damaged queue files are moved here
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for inspection.
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<b>DELIVERY</b> <b>STATUS</b> <b>REPORTS</b>
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The <b>qmgr</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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file:
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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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The <b>qmgr</b> daemon is responsible for asking the <a href="bounce.8.html"><b>bounce</b>(8)</a> or
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<a href="defer.8.html"><b>defer</b>(8)</a> daemons to send non-delivery reports.
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<b>STRATEGIES</b>
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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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(output).
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<b>leaky</b> <b>bucket</b>
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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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<b>fairness</b>
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When the <b>active</b> queue has room, the queue manager
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takes one message from the <b>incoming</b> queue 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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<b>slow</b> <b>start</b>
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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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<b>round</b> <b>robin</b>
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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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tions.
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<b>exponential</b> <b>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</b> <b>status</b> <b>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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<b>TRIGGERS</b>
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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</b> <b>(QMGR</b><i>_</i><b>REQ</b><i>_</i><b>SCAN</b><i>_</i><b>DEFERRED)</b>
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Start a deferred queue 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</b> <b>(QMGR</b><i>_</i><b>REQ</b><i>_</i><b>SCAN</b><i>_</i><b>INCOMING)</b>
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Start an incoming queue 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</b> <b>(QMGR</b><i>_</i><b>REQ</b><i>_</i><b>SCAN</b><i>_</i><b>ALL)</b>
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Ignore deferred queue file time stamps. The request
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affects the next deferred queue scan.
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<b>F</b> <b>(QMGR</b><i>_</i><b>REQ</b><i>_</i><b>FLUSH</b><i>_</i><b>DEAD)</b>
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Purge all information about dead transports and
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destinations.
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<b>W</b> <b>(TRIGGER</b><i>_</i><b>REQ</b><i>_</i><b>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 incoming queue
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scan.
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The <b>qmgr</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 deferred queue
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run, one would request <b>A</b> <b>F</b> <b>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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<b>STANDARDS</b>
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None. The <b>qmgr</b> daemon does not interact with the outside
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world.
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<b>SECURITY</b>
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The <b>qmgr</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>qmgr</b> daemon does not talk to the outside world, and it can
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be run at fixed low privilege in a chrooted environment.
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<b>DIAGNOSTICS</b>
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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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further inspection.
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Depending on the setting of the <b>notify</b><i>_</i><b>classes</b> parameter,
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the postmaster is notified of bounces and of other trou-
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ble.
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<b>BUGS</b>
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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</b> <b>PARAMETERS</b>
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The following <b>main.cf</b> parameters are especially relevant
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to this program. See the Postfix <b>main.cf</b> file for syntax
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details and for default values. Use the <b>postfix</b> <b>reload</b>
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command after a configuration change.
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<b>Miscellaneous</b>
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<b>allow</b><i>_</i><b>min</b><i>_</i><b>user</b>
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Do not bounce recipient addresses that begin with
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'-'.
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<b>relocated</b><i>_</i><b>maps</b>
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Tables with contact information for users, hosts or
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domains that no longer exist. See <a href="relocated.5.html"><b>relocated</b>(5)</a>.
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<b>queue</b><i>_</i><b>directory</b>
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Top-level directory of the Postfix queue.
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<b>Active</b> <b>queue</b> <b>controls</b>
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<b>qmgr</b><i>_</i><b>message</b><i>_</i><b>active</b><i>_</i><b>limit</b>
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Limit the number of messages in the active queue.
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<b>qmgr</b><i>_</i><b>message</b><i>_</i><b>recipient</b><i>_</i><b>limit</b>
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Limit the number of in-memory recipients.
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This parameter also limits the size of the short-
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term, in-memory destination cache.
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<b>Timing</b> <b>controls</b>
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<b>minimal</b><i>_</i><b>backoff</b><i>_</i><b>time</b>
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Minimal time in seconds between delivery attempts
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of a deferred message.
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This parameter also limits the time an unreachable
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destination is kept in the short-term, in-memory
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destination status cache.
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<b>maximal</b><i>_</i><b>backoff</b><i>_</i><b>time</b>
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Maximal time in seconds between delivery attempts
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of a deferred message.
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<b>maximal</b><i>_</i><b>queue</b><i>_</i><b>lifetime</b>
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Maximal time in days a message is queued before it
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is sent back as undeliverable.
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<b>queue</b><i>_</i><b>run</b><i>_</i><b>delay</b>
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Time in seconds between deferred queue scans. Queue
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scans do not overlap.
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<b>transport</b><i>_</i><b>retry</b><i>_</i><b>time</b>
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Time in seconds between attempts to contact a bro-
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ken delivery transport.
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<b>Concurrency</b> <b>controls</b>
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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>ter.cf</b> entry.
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<b>qmgr</b><i>_</i><b>fudge</b><i>_</i><b>factor</b> (valid range: 10..100)
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The percentage of delivery resources that a busy
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mail system will use up for delivery of a large
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mailing list message. With 100%, delivery of one
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message does not begin before the previous message
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has been delivered. This results in good perfor-
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mance for large mailing lists, but results in poor
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response time for one-to-one mail. With less than
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100%, response time for one-to-one mail improves,
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but large mailing list delivery performance suf-
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fers. In the worst case, recipients near the begin-
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ning of a large list receive a burst of messages
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immediately, while recipients near the end of that
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list receive that same burst of messages a whole
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day later.
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<b>qmgr</b><i>_</i><b>site</b><i>_</i><b>hog</b><i>_</i><b>factor</b> (valid range: 10..100)
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The percentage of delivery resources that a busy
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mail system will use up for delivery to a single
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site. With 100%, mail is delivered in first-in,
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first-out order, so that a burst of mail for one
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site can block mail for other destinations. With
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less than 100%, the excess mail is deferred. The
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deferred mail is delivered in little bursts, the
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remainder of the backlog being deferred again, with
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a lot of I/O activity happening as Postfix searches
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the deferred queue for deliverable mail.
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<b>initial</b><i>_</i><b>destination</b><i>_</i><b>concurrency</b>
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Initial per-destination concurrency level for par-
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allel delivery to the same destination.
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<b>default</b><i>_</i><b>destination</b><i>_</i><b>concurrency</b><i>_</i><b>limit</b>
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Default limit on the number of parallel deliveries
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to the same destination.
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<i>transport_</i><b>destination</b><i>_</i><b>concurrency</b><i>_</i><b>limit</b>
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Limit on the number of parallel deliveries to the
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same destination, for delivery via the named mes-
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sage <i>transport</i>.
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<b>Recipient</b> <b>controls</b>
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<b>default</b><i>_</i><b>destination</b><i>_</i><b>recipient</b><i>_</i><b>limit</b>
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Default limit on the number of recipients per mes-
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sage transfer.
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<i>transport_</i><b>destination</b><i>_</i><b>recipient</b><i>_</i><b>limit</b>
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Limit on the number of recipients per message
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transfer, for the named message <i>transport</i>.
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<b>SEE</b> <b>ALSO</b>
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<a href="master.8.html">master(8)</a>, process manager
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<a href="relocated.5.html">relocated(5)</a>, format of the "user has moved" table
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syslogd(8) system logging
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<a href="trivial-rewrite.8.html">trivial-rewrite(8)</a>, address routing
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<b>LICENSE</b>
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The Secure Mailer license must be distributed with this
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software.
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<b>AUTHOR(S)</b>
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Wietse Venema
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IBM T.J. Watson Research
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P.O. Box 704
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Yorktown Heights, NY 10598, USA
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QMGR(8)
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</pre> </body> </html>
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