    VERIFY(8)                                               VERIFY(8)

    NAME
           verify - Postfix address verification server

    SYNOPSIS
           verify [generic Postfix daemon options]

    DESCRIPTION
           The Postfix address verification server maintains a record
           of what recipient addresses are known to be deliverable or
           undeliverable.

           Addresses are verified by submitting probe messages to the
           Postfix queue. Probe messages  are  run  through  all  the
           routing and rewriting machinery except for final delivery,
           and are discarded rather than being deferred or bounced.

           Address verification relies on the answer from the nearest
           MTA  for  the  specified  address,  and will therefore not
           detect all undeliverable addresses.

           This server is designed to run under control by the  Post-
           fix  master  server.  It  maintains an optional persistent
           database.  To avoid being interrupted by "postfix stop" in
           the  middle  of  a  database update, the process runs in a
           separate process group.

           This server implements the following requests:

           VRFY_ADDR_UPDATE address status text
                  Update the status of the specified address.

           VRFY_ADDR_QUERY address
                  Look up  the  status  and  text  of  the  specified
                  address.  If the status is unknown, a probe is sent
                  and a default status is returned.

           The server reply status is one of:

           VRFY_STAT_OK
                  The request completed normally.

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

           VRFY_STAT_FAIL
                  The request failed.

           The recipient status is one of:

           DEL_RCPT_STAT_OK
                  The address is deliverable.

           DEL_RCPT_STAT_DEFER
                  The  address  is  undeliverable  due to a temporary
                  problem.

           DEL_RCPT_STAT_BOUNCE
                  The address is undeliverable  due  to  a  permanent
                  problem.

           DEL_RCPT_STAT_TODO
                  The address status is being determined.

    SECURITY
           The address verification server is not security-sensitive.
           It does not talk to the network, and it does not  talk  to
           local  users.  The verify server can run chrooted at fixed
           low privilege.

           The address verification server can be  coerced  to  store
           unlimited  amounts  of  garbage.  Limiting  the cache size
           trades one problem (disk space exhaustion) for another one
           (poor response time to client requests).

    DIAGNOSTICS
           Problems and transactions are logged to syslogd(8).

    BUGS
           If  the  persistent  database ever gets corrupted then the
           world comes to an end and human  intervention  is  needed.
           This violates a basic Postfix principle.

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

    Cache control
           address_verify_map
                  Optional  table  for  persistent  recipient  status
                  storage. The file  is  opened  before  the  process
                  enters a chroot jail and before it drops root priv-
                  ileges.  By default, the  information  is  kept  in
                  volatile  memory,  and is lost after postfix reload
                  or postfix stop.

                  To recover from a  corrupted  address  verification
                  database, delete the file and do postfix reload.

           address_verify_sender
                  The sender address to use for probe messages. Spec-
                  ify an empty value (address_verify_sender =) or  <>
                  if you want to use the null sender address.

           address_verify_positive_expire_time
                  The  amount  of time after which a known to be good
                  address expires.

           address_verify_positive_refresh_time
                  The minimal amount of time after which a  proactive
                  probe  is  sent  to  verify that a known to be good
                  address is still good. The address  status  is  not
                  updated  when the probe fails (optimistic caching).

           address_verify_negative_cache
                  A boolean parameter that controls whether  negative
                  probe  results  are stored in the address verifica-
                  tion cache. When enabled,  the  cache  may  pollute
                  quickly  with  garbage. When disabled, Postfix will
                  generate an address probe for every lookup.

           address_verify_negative_expire_time
                  The amount of time after which a  rejected  address
                  expires.

           address_verify_negative_refresh_time
                  The  minimal amount of time after which a proactive
                  probe is sent to verify that  a  known  to  be  bad
                  address is still bad.

    Probe message routing
           By  default,  probe  messages  are  delivered via the same
           route as regular messages.  The following  parameters  can
           be used to override specific message routing mechanisms.

           address_verify_relayhost
                  Overrides the relayhost setting.

           address_verify_transport_maps
                  Overrides the transport_maps setting.

           address_verify_local_transport
                  Overrides the local_transport setting.

           address_verify_virtual_transport
                  Overrides the virtual_transport setting.

           address_verify_relay_transport
                  Overrides the relay_transport setting.

           address_verify_default_transport
                  Overrides the default_transport setting.

    SEE ALSO
           trivial-rewrite(8) address rewriting and resolving

    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

                                                            VERIFY(8)