FLUSH(8)						      System Manager's Manual							  FLUSH(8)

NAME

       flush - Postfix fast flush server

SYNOPSIS

       flush [generic Postfix daemon options]

DESCRIPTION

       The  flush server maintains a record of deferred mail by destination.  This information is used to improve the performance of the SMTP ETRN
       request, and of its command-line equivalent, sendmail -qR.  This program 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  destinations  is  specified
       with the fast_flush_domains configuration parameter, which defaults to $relay_domains.

       This server implements the following requests:

       FLUSH_REQ_ADD sitename queue_id
	      Inform  the  fast flush server that the specified message is queued for sitename. Depending on logging policy, the fast flush server
	      stores or ignores the information.

       FLUSH_REQ_SEND sitename
	      Request delivery of mail that is queued for sitename.  If the destination is eligible for a fast flush logfile, this  request  trig-
	      gers  delivery  of messages listed in that destination's logfile, and the logfile is truncated to zero length; if mail is undeliver-
	      able it will be added back to the logfile.

	      If the destination is not eligible for a fast flush logfile, this request is rejected (see below for status codes).

       TRIGGER_REQ_WAKEUP
	      This wakeup request from the master is an alternative way to request FLUSH_REQ_REFRESH.

       FLUSH_REQ_REFRESH (completes in the background)
	      Refresh non-empty per-destination logfiles that were not read in fast_flush_refresh_time hours, by  simulating  send  requests  (see
	      above) for the corresponding destinations.

	      Delete empty per-destination logfiles that were not updated in fast_flush_purge_time days.

       FLUSH_REQ_PURGE (completes in the background)
	      Refresh  all  non-empty  per-destination logfiles, by simulating send requests (see above) for the corresponding destinations.  This
	      can be incredibly expensive when logging is enabled for many destinations, and is not recommended.

	      Delete empty per-destination logfiles that were not updated in fast_flush_purge_time days.

       The server response is one of:

       FLUSH_STAT_OK
	      The request completed normally.

       FLUSH_STAT_BAD
	      The flush server rejected the request (bad request name, bad request parameter value).

       FLUSH_STAT_FAIL
	      The request failed.

       FLUSH_STAT_DENY
	      The request was denied because the destination domain is not eligible for fast flush service, or because the fast flush  service	is
	      disabled.

SECURITY

       The  fast  flush  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 privilege.

DIAGNOSTICS

       Problems and transactions are logged to syslogd(8).

BUGS

       Fast flush logfiles are truncated only after a FLUSH_REQ_SEND request, not when mail is actually delivered, and	therefore  can	accumulate
       outdated  or  redundant	data.  In  order to maintain sanity, FLUSH_REQ_REFRESH must be executed periodically. This can be automated with a
       suitable wakeup timer setting in the master.cf configuration file.

       Upon receipt of a request to deliver all mail for an eligible destination, the flush 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 destination because such mail typically only has recipients in one domain.

FILES

       /var/spool/postfix/flush, location of "fast flush" logfiles.

CONFIGURATION PARAMETERS

       See the Postfix main.cf file for syntax details and for default values. Use the postfix reload command after a configuration change.

       fast_flush_domains
	      What destinations can have a "fast flush" logfile. By default, this is set to $relay_domains.

       fast_flush_refresh_time
	      Refresh a non-empty "fast flush" logfile that was not read in this amount of time (default time unit: hours), by simulating  a  send
	      request for the corresponding destination.

       fast_flush_purge_time
	      Remove an empty "fast flush" logfile that was not updated in this amount of time (default time unit: days).

       parent_domain_matches_subdomains
	      List of Postfix features that use domain.tld patterns to match sub.domain.tld (as opposed to requiring .domain.tld patterns).

SEE ALSO

       smtpd(8) Postfix SMTP server
       qmgr(8) Postfix queue manager
       syslogd(8) system logging

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

																	  FLUSH(8)