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<!doctype html public "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
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<title> Postfix manual - verify(8) </title>
</head> <body> <pre>
VERIFY(8) VERIFY(8)
<b>NAME</b>
verify - Postfix address verification server
<b>SYNOPSIS</b>
<b>verify</b> [generic Postfix daemon options]
<b>DESCRIPTION</b>
The <a href="verify.8.html"><b>verify</b>(8)</a> address verification server maintains a
record of what recipient addresses are known to be deliv-
erable 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 <a href="verify.8.html"><b>verify</b>(8)</a> server is designed to run under control by
the Postfix master server. It maintains an optional per-
sistent database. To avoid being interrupted by "postfix
stop" in the middle of a database update, the process runs
in a separate process group.
The <a href="verify.8.html"><b>verify</b>(8)</a> server implements the following requests:
<b>update</b> <i>address status text</i>
Update the status and text of the specified
address.
<b>query</b> <i>address</i>
Look up the <i>status</i> and <i>text</i> for the specified
address. If the status is unknown, a probe is sent
and an "in progress" status is returned.
<b>SECURITY</b>
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).
<b>DIAGNOSTICS</b>
Problems and transactions are logged to <b>syslogd</b>(8).
<b>BUGS</b>
The address verification service is suitable only for
sites that handle a low mail volume. Verification probes
add additional traffic to the mail queue and perform
poorly under high load. Servers may blacklist sites that
probe excessively, or that probe excessively for non-exis-
tent recipient addresses.
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.
<b>CONFIGURATION PARAMETERS</b>
Changes to <a href="postconf.5.html"><b>main.cf</b></a> are not picked up automatically, as
<a href="verify.8.html"><b>verify</b>(8)</a> processes are persistent. Use the command "<b>post-</b>
<b>fix reload</b>" after a configuration change.
The text below provides only a parameter summary. See
<a href="postconf.5.html"><b>postconf</b>(5)</a> for more details including examples.
<b>CACHE CONTROLS</b>
<b><a href="postconf.5.html#address_verify_map">address_verify_map</a> (empty)</b>
Optional lookup table for persistent address veri-
fication status storage.
<b><a href="postconf.5.html#address_verify_sender">address_verify_sender</a> (postmaster)</b>
The sender address to use in address verification
probes.
<b><a href="postconf.5.html#address_verify_positive_expire_time">address_verify_positive_expire_time</a> (31d)</b>
The time after which a successful probe expires
from the address verification cache.
<b><a href="postconf.5.html#address_verify_positive_refresh_time">address_verify_positive_refresh_time</a> (7d)</b>
The time after which a successful address verifica-
tion probe needs to be refreshed.
<b><a href="postconf.5.html#address_verify_negative_cache">address_verify_negative_cache</a> (yes)</b>
Enable caching of failed address verification probe
results.
<b><a href="postconf.5.html#address_verify_negative_expire_time">address_verify_negative_expire_time</a> (3d)</b>
The time after which a failed probe expires from
the address verification cache.
<b><a href="postconf.5.html#address_verify_negative_refresh_time">address_verify_negative_refresh_time</a> (3h)</b>
The time after which a failed address verification
probe needs to be refreshed.
<b>PROBE MESSAGE ROUTING CONTROLS</b>
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.
<b><a href="postconf.5.html#address_verify_relayhost">address_verify_relayhost</a> ($<a href="postconf.5.html#relayhost">relayhost</a>)</b>
Overrides the <a href="postconf.5.html#relayhost">relayhost</a> parameter setting for
address verification probes.
<b><a href="postconf.5.html#address_verify_transport_maps">address_verify_transport_maps</a> ($<a href="postconf.5.html#transport_maps">transport_maps</a>)</b>
Overrides the <a href="postconf.5.html#transport_maps">transport_maps</a> parameter setting for
address verification probes.
<b><a href="postconf.5.html#address_verify_local_transport">address_verify_local_transport</a> ($<a href="postconf.5.html#local_transport">local_transport</a>)</b>
Overrides the <a href="postconf.5.html#local_transport">local_transport</a> parameter setting for
address verification probes.
<b><a href="postconf.5.html#address_verify_virtual_transport">address_verify_virtual_transport</a> ($<a href="postconf.5.html#virtual_transport">virtual_transport</a>)</b>
Overrides the <a href="postconf.5.html#virtual_transport">virtual_transport</a> parameter setting
for address verification probes.
<b><a href="postconf.5.html#address_verify_relay_transport">address_verify_relay_transport</a> ($<a href="postconf.5.html#relay_transport">relay_transport</a>)</b>
Overrides the <a href="postconf.5.html#relay_transport">relay_transport</a> parameter setting for
address verification probes.
<b><a href="postconf.5.html#address_verify_default_transport">address_verify_default_transport</a> ($<a href="postconf.5.html#default_transport">default_transport</a>)</b>
Overrides the <a href="postconf.5.html#default_transport">default_transport</a> parameter setting
for address verification probes.
<b>MISCELLANEOUS CONTROLS</b>
<b><a href="postconf.5.html#config_directory">config_directory</a> (see 'postconf -d' output)</b>
The default location of the Postfix <a href="postconf.5.html">main.cf</a> and
<a href="master.5.html">master.cf</a> configuration files.
<b><a href="postconf.5.html#daemon_timeout">daemon_timeout</a> (18000s)</b>
How much time a Postfix daemon process may take to
handle a request before it is terminated by a
built-in watchdog timer.
<b><a href="postconf.5.html#ipc_timeout">ipc_timeout</a> (3600s)</b>
The time limit for sending or receiving information
over an internal communication channel.
<b><a href="postconf.5.html#process_id">process_id</a> (read-only)</b>
The process ID of a Postfix command or daemon
process.
<b><a href="postconf.5.html#process_name">process_name</a> (read-only)</b>
The process name of a Postfix command or daemon
process.
<b><a href="postconf.5.html#queue_directory">queue_directory</a> (see 'postconf -d' output)</b>
The location of the Postfix top-level queue direc-
tory.
<b><a href="postconf.5.html#syslog_facility">syslog_facility</a> (mail)</b>
The syslog facility of Postfix logging.
<b><a href="postconf.5.html#syslog_name">syslog_name</a> (postfix)</b>
The mail system name that is prepended to the
process name in syslog records, so that "smtpd"
becomes, for example, "postfix/smtpd".
<b>SEE ALSO</b>
<a href="smtpd.8.html">smtpd(8)</a>, Postfix SMTP server
<a href="cleanup.8.html">cleanup(8)</a>, enqueue Postfix message
<a href="postconf.5.html">postconf(5)</a>, configuration parameters
syslogd(5), system logging
<b>README FILES</b>
<a href="ADDRESS_VERIFICATION_README.html">ADDRESS_VERIFICATION_README</a>, address verification howto
<b>LICENSE</b>
The Secure Mailer license must be distributed with this
software.
<b>HISTORY</b>
This service was introduced with Postfix version 2.1.
<b>AUTHOR(S)</b>
Wietse Venema
IBM T.J. Watson Research
P.O. Box 704
Yorktown Heights, NY 10598, USA
VERIFY(8)
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