flush - Postfix fast flush server
flush [generic Postfix daemon options]
The flush(8) server maintains a record of deferred mail by
destination. This information is used to improve the per-
formance of the SMTP ETRN request, and of its command-line
equivalent, "sendmail -qR" or "postqueue -f". This pro-
gram expects to be run from the master(8) process manager.
The record is implemented as a per-destination logfile
with as contents the queue IDs of deferred mail. A logfile
is append-only, and is truncated when delivery is
requested for the corresponding destination. A destination
is the part on the right-hand side of the right-most @ in
an email address.
Per-destination logfiles of deferred mail are maintained
only for eligible destinations. The list of eligible des-
tinations is specified with the fast_flush_domains config-
uration parameter, which defaults to $relay_domains.
This server implements the following requests:
add sitename queueid
Inform the flush(8) server that the message with
the specified queue ID is queued for the specified
Request delivery of mail that is queued for the
Refresh non-empty per-destination logfiles that
were not read in $fast_flush_refresh_time hours, by
simulating send requests (see above) for the corre-
Delete empty per-destination logfiles that were not
updated in $fast_flush_purge_time days.
This request completes in the background.
purge Do a refresh for all per-destination logfiles.
The flush(8) server is not security-sensitive. It does not
talk to the network, and it does not talk to local users.
The fast flush server can run chrooted at fixed low privi-
Problems and transactions are logged to syslogd(8).
Fast flush logfiles are truncated only after a "send"
request, not when mail is actually delivered, and there-
fore can accumulate outdated or redundant data. In order
to maintain sanity, "refresh" must be executed periodi-
cally. This can be automated with a suitable wakeup timer
setting in the master.cf configuration file.
Upon receipt of a request to deliver mail for an eligible
destination, the flush(8) server requests delivery of all
messages that are listed in that destination's logfile,
regardless of the recipients of those messages. This is
not an issue for mail that is sent to a relay_domains des-
tination because such mail typically only has recipients
in one domain.
Changes to main.cf are picked up automatically as flush(8)
processes run for only a limited amount of time. Use the
command "postfix reload" to speed up a change.
The text below provides only a parameter summary. See
postconf(5) for more details including examples.
config_directory (see 'postconf -d' output)
The default location of the Postfix main.cf and
master.cf configuration files.
How much time a Postfix daemon process may take to
handle a request before it is terminated by a
built-in watchdog timer.
Optional list of destinations that are eligible for
per-destination logfiles with mail that is queued
to those destinations.
The time after which a non-empty but unread per-
destination "fast flush" logfile needs to be
The time after which an empty per-destination "fast
flush" logfile is deleted.
The time limit for sending or receiving information
over an internal communication channel.
The maximum amount of time that an idle Postfix
daemon process waits for the next service request
The maximal number of connection requests before a
Postfix daemon process terminates.
parent_domain_matches_subdomains (see 'postconf -d' out-
What Postfix features match subdomains of
"domain.tld" automatically, instead of requiring an
explicit ".domain.tld" pattern.
The process ID of a Postfix command or daemon
The process name of a Postfix command or daemon
queue_directory (see 'postconf -d' output)
The location of the Postfix top-level queue direc-
The syslog facility of Postfix logging.
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/flush, "fast flush" logfiles.
smtpd(8), SMTP server
qmgr(8), queue manager
postconf(5), configuration parameters
master(5), generic daemon options
master(8), process manager
syslogd(8), system logging
ETRN_README, Postfix ETRN howto
The Secure Mailer license must be distributed with this
This service was introduced with Postfix version 1.0.
IBM T.J. Watson Research
P.O. Box 704
Yorktown Heights, NY 10598, USA