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

       flush - Postfix fast flush server

       flush [generic Postfix daemon options]

       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 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 trun-
       cated 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  eli-
       gible destinations. The list of eligible destinations is specified with
       the  fast_flush_domains  configuration  parameter,  which  defaults  to

       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
              triggers  delivery of messages listed in that destination's log-
              file, and the logfile is truncated to zero length;  if  mail  is
              undeliverable 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).

              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:

              The request completed normally.

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

              The request failed.

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

       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.

       Problems and transactions are logged to syslogd(8).

       Fast  flush logfiles are truncated only after a FLUSH_REQ_SEND request,
       not when mail is actually delivered, and therefore can accumulate  out-
       dated 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 destina-
       tion, 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 recipi-
       ents in one domain.

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

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

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

              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.

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

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

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

       The Secure Mailer license must be distributed with this software.

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