Ubuntu Manpage: verify - Postfix address verification server

Provided by: postfix_3.3.0-1ubuntu0.4_amd64

NAME

       verify - Postfix address verification server

SYNOPSIS

       verify [generic Postfix daemon options]

DESCRIPTION

       The  verify(8) address verification server maintains a record of what recipient addresses are known to be
       deliverable or undeliverable.

       Addresses are verified by injecting probe messages into 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.

       The  verify(8)  server  is  designed  to  run under control by the Postfix 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.

       The verify(8) server implements the following requests:

       update address status text
              Update the status and text of the specified address.

       query address
              Look  up the status and text for the specified address.  If the status is unknown, a probe is sent
              and an "in progress" status is returned.

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
       expiry time trades one problem (disk space exhaustion) for another one  (poor  response  time  to  client
       requests).

       With  Postfix version 2.5 and later, the verify(8) server no longer uses root privileges when opening the
       address_verify_map cache file. The file should now be stored under the Postfix-owned data_directory.   As
       a  migration  aid,  an  attempt  to  open a cache file under a non-Postfix directory is redirected to the
       Postfix-owned data_directory, and a warning is logged.

DIAGNOSTICS

       Problems and transactions are logged to syslogd(8).

BUGS

       Address verification probe messages add additional traffic to the mail queue.  Recipient verification may
       cause  an  increased  load  on  down-stream  servers  in  the  case  of a dictionary attack or a flood of
       backscatter bounces.  Sender address  verification  may  cause  your  site  to  be  blacklisted  by  some
       providers.

       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

       Changes to main.cf are not picked up automatically,  as  verify(8)  processes  are  long-lived.  Use  the
       command "postfix reload" after a configuration change.

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

PROBE MESSAGE CONTROLS

       address_verify_sender ($double_bounce_sender)
              The  sender  address  to  use in address verification probes; prior to Postfix 2.5 the default was
              "postmaster".

       Available with Postfix 2.9 and later:

       address_verify_sender_ttl (0s)
              The time between changes in the  time-dependent  portion  of  address  verification  probe  sender
              addresses.

CACHE CONTROLS

       address_verify_map (see 'postconf -d' output)
              Lookup table for persistent address verification status storage.

       address_verify_positive_expire_time (31d)
              The time after which a successful probe expires from the address verification cache.

       address_verify_positive_refresh_time (7d)
              The time after which a successful address verification probe needs to be refreshed.

       address_verify_negative_cache (yes)
              Enable caching of failed address verification probe results.

       address_verify_negative_expire_time (3d)
              The time after which a failed probe expires from the address verification cache.

       address_verify_negative_refresh_time (3h)
              The time after which a failed address verification probe needs to be refreshed.

       Available with Postfix 2.7 and later:

       address_verify_cache_cleanup_interval (12h)
              The amount of time between verify(8) address verification database cleanup runs.

PROBE MESSAGE ROUTING CONTROLS

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 ($relayhost)
Overrides the relayhost parameter setting for address verification probes.

address_verify_transport_maps ($transport_maps)
Overrides the transport_maps parameter setting for address verification probes.

address_verify_local_transport ($local_transport)
Overrides the local_transport parameter setting for address verification probes.

address_verify_virtual_transport ($virtual_transport)
Overrides the virtual_transport parameter setting for address verification probes.

address_verify_relay_transport ($relay_transport)
Overrides the relay_transport parameter setting for address verification probes.

address_verify_default_transport ($default_transport)
Overrides the default_transport parameter setting for address verification probes.

Available in Postfix 2.3 and later:

address_verify_sender_dependent_relayhost_maps ($sender_dependent_relayhost_maps)
Overrides the sender_dependent_relayhost_maps parameter setting for address verification probes.

Available in Postfix 2.7 and later:

address_verify_sender_dependent_default_transport_maps ($sender_dependent_default_transport_maps)
Overrides the sender_dependent_default_transport_maps parameter setting for address verification
probes.

SMTPUTF8 CONTROLS

       Preliminary SMTPUTF8 support is introduced with Postfix 3.0.

       smtputf8_autodetect_classes (sendmail, verify)
              Detect that a message requires SMTPUTF8 support for the specified mail origin classes.

       Available in Postfix version 3.2 and later:

       enable_idna2003_compatibility (no)
              Enable  'transitional'  compatibility  between IDNA2003 and IDNA2008, when converting UTF-8 domain
              names to/from the ASCII form that is used for DNS lookups.

MISCELLANEOUS CONTROLS

       config_directory (see 'postconf -d' output)
              The default location of the Postfix main.cf and master.cf configuration files.

       daemon_timeout (18000s)
              How much time a Postfix daemon process may take to handle a request before it is terminated  by  a
              built-in watchdog timer.

       ipc_timeout (3600s)
              The time limit for sending or receiving information over an internal communication channel.

       process_id (read-only)
              The process ID of a Postfix command or daemon process.

       process_name (read-only)
              The process name of a Postfix command or daemon process.

       queue_directory (see 'postconf -d' output)
              The location of the Postfix top-level queue directory.

       syslog_facility (mail)
              The syslog facility of Postfix logging.

       syslog_name (see 'postconf -d' output)
              A  prefix  that  is prepended to the process name in syslog records, so that, for example, "smtpd"
              becomes "prefix/smtpd".

       Available in Postfix 3.3 and later:

       service_name (read-only)
              The master.cf service name of a Postfix daemon process.

README FILES

       Use "postconf readme_directory" or "postconf html_directory" to locate this information.
       ADDRESS_VERIFICATION_README, address verification howto

LICENSE

       The Secure Mailer license must be distributed with this software.

HISTORY

       This service was introduced with Postfix version 2.1.

AUTHOR(S)

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

       Wietse Venema
       Google, Inc.
       111 8th Avenue
       New York, NY 10011, USA

                                                                                                VERIFY(8postfix)