qmgr [generic Postfix daemon options]

Mail addressed to the local double-bounce address is logged and discarded. This stops potential loops caused by undeliverable bounce notifications.  

incoming

Inbound mail from the network, or mail picked up by the local pickup(8) daemon 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.

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 qmgr(8) daemon is responsible for asking the bounce(8), defer(8) or trace(8) daemons to send delivery reports.  

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.

preemptive message scheduling

The queue manager attempts to minimize the average per-recipient delay while still preserving the correct per-message delays, using a sophisticated preemptive message scheduling.

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 qmgr(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.  

RFC 3463 (Enhanced status codes)
RFC 3464 (Delivery status notifications)

Depending on the setting of the notify_classes parameter, the postmaster is notified of bounces and of other trouble.  

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.  

allow_min_user (no)

Allow a sender or recipient address to have `-' as the first character.

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.

qmgr_message_recipient_minimum (10)

The minimal number of in-memory recipients for any message.

default_recipient_limit (20000)

The default per-transport upper limit on the number of in-memory recipients.

transport_recipient_limit ($default_recipient_limit)

Idem, for delivery via the named message transport.

default_extra_recipient_limit (1000)

The default value for the extra per-transport limit imposed on the number of in-memory recipients.

transport_extra_recipient_limit ($default_extra_recipient_limit)

Idem, for delivery via the named message transport.

Available in Postfix version 2.4 and later:

default_recipient_refill_limit (100)

The default per-transport limit on the number of recipients refilled at once.

transport_recipient_refill_limit ($default_recipient_refill_limit)

Idem, for delivery via the named message transport.

default_recipient_refill_delay (5s)

The default per-transport maximum delay between recipients refills.

transport_recipient_refill_delay ($default_recipient_refill_delay)

Idem, for delivery via the named message transport.

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.

default_destination_recipient_limit (50)

The default maximal number of recipients per message delivery.

transport_destination_recipient_limit ($default_destination_recipient_limit)

Idem, for delivery via the named message transport.

default_delivery_slot_cost (5)

How often the Postfix queue manager's scheduler is allowed to preempt delivery of one message with another.

transport_delivery_slot_cost ($default_delivery_slot_cost)

Idem, for delivery via the named message transport.

default_minimum_delivery_slots (3)

How many recipients a message must have in order to invoke the Postfix queue manager's scheduling algorithm at all.

transport_minimum_delivery_slots ($default_minimum_delivery_slots)

Idem, for delivery via the named message transport.

default_delivery_slot_discount (50)

The default value for transport-specific _delivery_slot_discount settings.

transport_delivery_slot_discount ($default_delivery_slot_discount)

Idem, for delivery via the named message transport.

default_delivery_slot_loan (3)

The default value for transport-specific _delivery_slot_loan settings.

transport_delivery_slot_loan ($default_delivery_slot_loan)

Idem, for delivery via the named message transport.

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)

The maximal time a message is queued before it is sent back as undeliverable.

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)

The maximal time a bounce message is queued before it is considered undeliverable.

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; with per-destination recipient limit > 1, a destination is a domain, otherwise it is a recipient.

transport_destination_rate_delay $default_destination_rate_delay

Idem, for delivery via the named message transport.

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".

/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

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

SCHEDULER_README, scheduling algorithm
QSHAPE_README, Postfix queue analysis

Wietse Venema
IBM T.J. Watson Research
P.O. Box 704
Yorktown Heights, NY 10598, USA

Preemptive scheduler enhancements:
Patrik Rak
Modra 6
155 00, Prague, Czech Republic

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

MESSAGE SCHEDULING CONTROLS

OTHER RESOURCE AND RATE CONTROLS

MISCELLANEOUS CONTROLS

FILES

SEE ALSO

README FILES

LICENSE

AUTHOR(S)