NAME

qmgr - Postfix queue manager

SYNOPSIS


qqmmggrr [generic Postfix daemon options]

DESCRIPTION

The qqmmggrr(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 ttrriivviiaall--rreewwrriittee(8) daemon. This program expects to be run from the mmaasstteerr(8) process manager.

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

MAIL QUEUES



The qqmmggrr(8) daemon maintains the following queues:
iinnccoommiinngg Inbound mail from the network, or mail picked up by the
local ppiicckkuupp(8) daemon from the mmaaiillddrroopp directory.
aaccttiivvee Messages that the queue manager has opened for delivery. Only
a limited number of messages is allowed to enter the aaccttiivvee queue (leaky bucket strategy, for a fixed delivery rate).
ddeeffeerrrreedd Mail that could not be delivered upon the first attempt. The queue
manager implements exponential backoff by doubling the time between delivery attempts.
ccoorrrruupptt Unreadable or damaged queue files are moved here for inspection.
hhoolldd Messages that are kept "on hold" are kept here until someone
sets them free.

DELIVERY STATUS REPORTS



The qqmmggrr(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:
bboouunnccee Per-recipient status information about why mail is bounced.
These files are maintained by the bboouunnccee(8) daemon.
ddeeffeerr Per-recipient status information about why mail is delayed.
These files are maintained by the ddeeffeerr(8) daemon.
ttrraaccee Per-recipient status information as requested with the
Postfix "sseennddmmaaiill --vv" or "sseennddmmaaiill --bbvv" command. These files are maintained by the ttrraaccee(8) daemon.

The qqmmggrr(8) daemon is responsible for asking the bboouunnccee(8), ddeeffeerr(8) or ttrraaccee(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).
lleeaakkyy bbuucckkeett This strategy limits the number of messages in the aaccttiivvee queue
and prevents the queue manager from running out of memory under heavy load.
ffaaiirrnneessss When the aaccttiivvee queue has room, the queue manager takes one
message from the iinnccoommiinngg queue and one from the ddeeffeerrrreedd queue. This prevents a large mail backlog from blocking the delivery of new mail.
ssllooww ssttaarrtt This strategy eliminates "thundering herd" problems by slowly
adjusting the number of parallel deliveries to the same destination.
rroouunndd rroobbiinn The queue manager sorts delivery requests by destination.
Round-robin selection prevents one destination from dominating deliveries to other destinations.
eexxppoonneennttiiaall bbaacckkooffff Mail that cannot be delivered upon the first attempt is deferred.
The time interval between delivery attempts is doubled after each attempt.
ddeessttiinnaattiioonn ssttaattuuss ccaacchhee The queue manager avoids unnecessary delivery attempts by
maintaining a short-term, in-memory list of unreachable destinations.
pprreeeemmppttiivvee mmeessssaaggee sscchheedduulliinngg 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.

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):
DD ((QQMMGGRR__RREEQQ__SSCCAANN__DDEEFFEERRRREEDD)) Start a deferred queue scan. If a deferred queue scan is already
in progress, that scan will be restarted as soon as it finishes.
II ((QQMMGGRR__RREEQQ__SSCCAANN__IINNCCOOMMIINNGG)) Start an incoming queue scan. If an incoming queue scan is already
in progress, that scan will be restarted as soon as it finishes.
AA ((QQMMGGRR__RREEQQ__SSCCAANN__AALLLL)) Ignore deferred queue file time stamps. The request affects
the next deferred queue scan.
FF ((QQMMGGRR__RREEQQ__FFLLUUSSHH__DDEEAADD)) Purge all information about dead transports and destinations.
WW ((TTRRIIGGGGEERR__RREEQQ__WWAAKKEEUUPP)) 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 qqmmggrr(8) daemon reads an entire buffer worth of triggers. Multiple identical trigger requests are collapsed into one, and trigger requests are sorted so that AA and FF precede DD and II. Thus, in order to force a deferred queue run, one would request AA FF DD; in order to notify the queue manager of the arrival of new mail one would request II.

STANDARDS


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

SECURITY



The qqmmggrr(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 qqmmggrr(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 daemon. Corrupted message files are saved to the ccoorrrruupptt queue for further inspection.

Depending on the setting of the nnoottiiffyy__ccllaasssseess 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 cclleeaannuupp(8). A sudden burst of inbound mail can negatively impact outbound delivery rates.

CONFIGURATION PARAMETERS



Changes to mmaaiinn..ccff are not picked up automatically
as qqmmggrr(8)
is a persistent process. Use the "ppoossttffiixx rreellooaadd" command after
a configuration change.
        

The text below provides only a parameter summary. See ppoossttccoonnff(5) for more details including examples.

In the text below, _t_r_a_n_s_p_o_r_t is the first field in a mmaasstteerr..ccff entry.

COMPATIBILITY CONTROLS



Available before Postfix version 2.5:
aallllooww__mmiinn__uusseerr ((nnoo)) Allow a sender or recipient address to have `-' as the first
character.

Available with Postfix version 2.7 and later:

ddeeffaauulltt__ffiilltteerr__nneexxtthhoopp ((eemmppttyy)) 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



qqmmggrr__cclloogg__wwaarrnn__ttiimmee ((330000ss)) The minimal delay between warnings that a specific destination is
clogging up the Postfix active queue.
qqmmggrr__mmeessssaaggee__aaccttiivvee__lliimmiitt ((2200000000)) The maximal number of messages in the active queue.
qqmmggrr__mmeessssaaggee__rreecciippiieenntt__lliimmiitt ((2200000000)) 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.
qqmmggrr__mmeessssaaggee__rreecciippiieenntt__mmiinniimmuumm ((1100)) The minimal number of in-memory recipients for any message.
ddeeffaauulltt__rreecciippiieenntt__lliimmiitt ((2200000000)) The default per-transport upper limit on the number of in-memory
recipients.
_t_r_a_n_s_p_o_r_t__rreecciippiieenntt__lliimmiitt (($$ddeeffaauulltt__rreecciippiieenntt__lliimmiitt)) Idem, for delivery via the named message _t_r_a_n_s_p_o_r_t.
ddeeffaauulltt__eexxttrraa__rreecciippiieenntt__lliimmiitt ((11000000)) The default value for the extra per-transport limit imposed on the
number of in-memory recipients.
_t_r_a_n_s_p_o_r_t__eexxttrraa__rreecciippiieenntt__lliimmiitt (($$ddeeffaauulltt__eexxttrraa__rreecciippiieenntt__lliimmiitt)) Idem, for delivery via the named message _t_r_a_n_s_p_o_r_t.

Available in Postfix version 2.4 and later:

ddeeffaauulltt__rreecciippiieenntt__rreeffiillll__lliimmiitt ((110000)) The default per-transport limit on the number of recipients refilled at
once.
_t_r_a_n_s_p_o_r_t__rreecciippiieenntt__rreeffiillll__lliimmiitt (($$ddeeffaauulltt__rreecciippiieenntt__rreeffiillll__lliimmiitt)) Idem, for delivery via the named message _t_r_a_n_s_p_o_r_t.
ddeeffaauulltt__rreecciippiieenntt__rreeffiillll__ddeellaayy ((55ss)) The default per-transport maximum delay between recipients refills.
_t_r_a_n_s_p_o_r_t__rreecciippiieenntt__rreeffiillll__ddeellaayy (($$ddeeffaauulltt__rreecciippiieenntt__rreeffiillll__ddeellaayy)) Idem, for delivery via the named message _t_r_a_n_s_p_o_r_t.

DELIVERY CONCURRENCY CONTROLS



iinniittiiaall__ddeessttiinnaattiioonn__ccoonnccuurrrreennccyy ((55)) The initial per-destination concurrency level for parallel delivery
to the same destination.
ddeeffaauulltt__ddeessttiinnaattiioonn__ccoonnccuurrrreennccyy__lliimmiitt ((2200)) The default maximal number of parallel deliveries to the same
destination.
_t_r_a_n_s_p_o_r_t__ddeessttiinnaattiioonn__ccoonnccuurrrreennccyy__lliimmiitt (($$ddeeffaauulltt__ddeessttiinnaattiioonn__ccoonnccuurrrreennccyy__lliimmiitt)) Idem, for delivery via the named message _t_r_a_n_s_p_o_r_t.

Available in Postfix version 2.5 and later:

_t_r_a_n_s_p_o_r_t__iinniittiiaall__ddeessttiinnaattiioonn__ccoonnccuurrrreennccyy (($$iinniittiiaall__ddeessttiinnaattiioonn__ccoonnccuurrrreennccyy)) Initial concurrency for delivery via the named message
_t_r_a_n_s_p_o_r_t.
ddeeffaauulltt__ddeessttiinnaattiioonn__ccoonnccuurrrreennccyy__ffaaiilleedd__ccoohhoorrtt__lliimmiitt ((11)) How many pseudo-cohorts must suffer connection or handshake
failure before a specific destination is considered unavailable (and further delivery is suspended).
_t_r_a_n_s_p_o_r_t__ddeessttiinnaattiioonn__ccoonnccuurrrreennccyy__ffaaiilleedd__ccoohhoorrtt__lliimmiitt (($$ddeeffaauulltt__ddeessttiinnaattiioonn__ccoonnccuurrrreennccyy__ffaaiilleedd__ccoohhoorrtt__lliimmiitt)) Idem, for delivery via the named message _t_r_a_n_s_p_o_r_t.
ddeeffaauulltt__ddeessttiinnaattiioonn__ccoonnccuurrrreennccyy__nneeggaattiivvee__ffeeeeddbbaacckk ((11)) The per-destination amount of delivery concurrency negative
feedback, after a delivery completes with a connection or handshake failure.
_t_r_a_n_s_p_o_r_t__ddeessttiinnaattiioonn__ccoonnccuurrrreennccyy__nneeggaattiivvee__ffeeeeddbbaacckk (($$ddeeffaauulltt__ddeessttiinnaattiioonn__ccoonnccuurrrreennccyy__nneeggaattiivvee__ffeeeeddbbaacckk)) Idem, for delivery via the named message _t_r_a_n_s_p_o_r_t.
ddeeffaauulltt__ddeessttiinnaattiioonn__ccoonnccuurrrreennccyy__ppoossiittiivvee__ffeeeeddbbaacckk ((11)) The per-destination amount of delivery concurrency positive
feedback, after a delivery completes without connection or handshake failure.
_t_r_a_n_s_p_o_r_t__ddeessttiinnaattiioonn__ccoonnccuurrrreennccyy__ppoossiittiivvee__ffeeeeddbbaacckk (($$ddeeffaauulltt__ddeessttiinnaattiioonn__ccoonnccuurrrreennccyy__ppoossiittiivvee__ffeeeeddbbaacckk)) Idem, for delivery via the named message _t_r_a_n_s_p_o_r_t.
ddeessttiinnaattiioonn__ccoonnccuurrrreennccyy__ffeeeeddbbaacckk__ddeebbuugg ((nnoo)) Make the queue manager's feedback algorithm verbose for performance
analysis purposes.

RECIPIENT SCHEDULING CONTROLS



ddeeffaauulltt__ddeessttiinnaattiioonn__rreecciippiieenntt__lliimmiitt ((5500)) The default maximal number of recipients per message delivery.
_t_r_a_n_s_p_o_r_t__ddeessttiinnaattiioonn__rreecciippiieenntt__lliimmiitt (($$ddeeffaauulltt__ddeessttiinnaattiioonn__rreecciippiieenntt__lliimmiitt)) Idem, for delivery via the named message _t_r_a_n_s_p_o_r_t.

MESSAGE SCHEDULING CONTROLS



ddeeffaauulltt__ddeelliivveerryy__sslloott__ccoosstt ((55)) How often the Postfix queue manager's scheduler is allowed to
preempt delivery of one message with another.
_t_r_a_n_s_p_o_r_t__ddeelliivveerryy__sslloott__ccoosstt (($$ddeeffaauulltt__ddeelliivveerryy__sslloott__ccoosstt)) Idem, for delivery via the named message _t_r_a_n_s_p_o_r_t.
ddeeffaauulltt__mmiinniimmuumm__ddeelliivveerryy__sslloottss ((33)) How many recipients a message must have in order to invoke the
Postfix queue manager's scheduling algorithm at all.
_t_r_a_n_s_p_o_r_t__mmiinniimmuumm__ddeelliivveerryy__sslloottss (($$ddeeffaauulltt__mmiinniimmuumm__ddeelliivveerryy__sslloottss)) Idem, for delivery via the named message _t_r_a_n_s_p_o_r_t.
ddeeffaauulltt__ddeelliivveerryy__sslloott__ddiissccoouunntt ((5500)) The default value for transport-specific _delivery_slot_discount
settings.
_t_r_a_n_s_p_o_r_t__ddeelliivveerryy__sslloott__ddiissccoouunntt (($$ddeeffaauulltt__ddeelliivveerryy__sslloott__ddiissccoouunntt)) Idem, for delivery via the named message _t_r_a_n_s_p_o_r_t.
ddeeffaauulltt__ddeelliivveerryy__sslloott__llooaann ((33)) The default value for transport-specific _delivery_slot_loan
settings.
_t_r_a_n_s_p_o_r_t__ddeelliivveerryy__sslloott__llooaann (($$ddeeffaauulltt__ddeelliivveerryy__sslloott__llooaann)) Idem, for delivery via the named message _t_r_a_n_s_p_o_r_t.

OTHER RESOURCE AND RATE CONTROLS



mmiinniimmaall__bbaacckkooffff__ttiimmee ((330000ss)) The minimal time between attempts to deliver a deferred message;
prior to Postfix 2.4 the default value was 1000s.
mmaaxxiimmaall__bbaacckkooffff__ttiimmee ((44000000ss)) The maximal time between attempts to deliver a deferred message.
mmaaxxiimmaall__qquueeuuee__lliiffeettiimmee ((55dd)) The maximal time a message is queued before it is sent back as
undeliverable.
qquueeuuee__rruunn__ddeellaayy ((330000ss)) The time between deferred queue scans by the queue manager;
prior to Postfix 2.4 the default value was 1000s.
ttrraannssppoorrtt__rreettrryy__ttiimmee ((6600ss)) The time between attempts by the Postfix queue manager to contact
a malfunctioning message delivery transport.

Available in Postfix version 2.1 and later:

bboouunnccee__qquueeuuee__lliiffeettiimmee ((55dd)) The maximal time a bounce message is queued before it is considered
undeliverable.

Available in Postfix version 2.5 and later:

ddeeffaauulltt__ddeessttiinnaattiioonn__rraattee__ddeellaayy ((00ss)) 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.
_t_r_a_n_s_p_o_r_t__ddeessttiinnaattiioonn__rraattee__ddeellaayy $$ddeeffaauulltt__ddeessttiinnaattiioonn__rraattee__ddeellaayy<> IIddeemm,, ffoorr ddeelliivveerryy vviiaa tthhee nnaammeedd mmeessssaaggee _t_r_a_n_s_p_o_r_t.

MISCELLANEOUS CONTROLS



ccoonnffiigg__ddiirreeccttoorryy ((sseeee ''ppoossttccoonnff --dd'' oouuttppuutt)) The default location of the Postfix main.cf and master.cf
configuration files.
ddeeffeerr__ttrraannssppoorrttss ((eemmppttyy)) The names of message delivery transports that should not deliver mail
unless someone issues "sseennddmmaaiill --qq" or equivalent.
ddeellaayy__llooggggiinngg__rreessoolluuttiioonn__lliimmiitt ((22)) The maximal number of digits after the decimal point when logging
sub-second delay values.
hheellppffuull__wwaarrnniinnggss ((yyeess)) Log warnings about problematic configuration settings, and provide
helpful suggestions.
iippcc__ttiimmeeoouutt ((33660000ss)) The time limit for sending or receiving information over an internal
communication channel.
pprroocceessss__iidd ((rreeaadd--oonnllyy)) The process ID of a Postfix command or daemon process.
pprroocceessss__nnaammee ((rreeaadd--oonnllyy)) The process name of a Postfix command or daemon process.
qquueeuuee__ddiirreeccttoorryy ((sseeee ''ppoossttccoonnff --dd'' oouuttppuutt)) The location of the Postfix top-level queue directory.
ssyysslloogg__ffaacciilliittyy ((mmaaiill)) The syslog facility of Postfix logging.
ssyysslloogg__nnaammee ((sseeee ''ppoossttccoonnff --dd'' oouuttppuutt)) The mail system name that is prepended to the process name in syslog
records, so that "smtpd" becomes, for example, "postfix/smtpd".

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 "ppoossttccoonnff rreeaaddmmee__ddiirreeccttoorryy" or
"ppoossttccoonnff hhttmmll__ddiirreeccttoorryy" to locate this information.

SCHEDULER_README, scheduling algorithm
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

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