verify(8) - man - phpMan

VERIFY(8postfix)                                                                    VERIFY(8postfix)



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 dis‐
       carded 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 main‐
       tains 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 privi‐
       lege.

       The address verification server can be coerced to store unlimited amounts of garbage.  Limit‐
       ing  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 Post‐
       fix-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) or postlogd(8).

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

       If  the  persistent database ever gets corrupted then the world comes to an end and human in‐
       tervention 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 de‐
              fault 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 follow‐
       ing 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 verifica‐
              tion probes.

       Available in Postfix 2.7 and later:

       address_verify_sender_dependent_default_transport_maps      ($sender_dependent_default_trans‐‐
       port_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 ter‐
              minated 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 exam‐
              ple, "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.

SEE ALSO
       smtpd(8), Postfix SMTP server
       cleanup(8), enqueue Postfix message
       postconf(5), configuration parameters
       postlogd(8), Postfix logging
       syslogd(8), system logging

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)