1VERIFY(8) System Manager's Manual VERIFY(8)
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6 verify - Postfix address verification server
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9 verify [generic Postfix daemon options]
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12 The verify(8) address verification server maintains a record of what
13 recipient addresses are known to be deliverable or undeliverable.
14 Addresses are verified by injecting probe messages into the Postfix
16 queue. Probe messages are run through all the routing and rewriting
17 machinery except for final delivery, and are discarded rather than
18 being deferred or bounced.
19 Address verification relies on the answer from the nearest MTA for the
21 specified address, and will therefore not detect all undeliverable
22 addresses.
23 The verify(8) server is designed to run under control by the Postfix
25 master server. It maintains an optional persistent database. To avoid
26 being interrupted by "postfix stop" in the middle of a database update,
27 the process runs in a separate process group.
28 The verify(8) server implements the following requests:
30 update address status text
32 Update the status and text of the specified address.
33 query address
35 Look up the status and text for the specified address. If the
36 status is unknown, a probe is sent and an "in progress" status
37 is returned.
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40 The address verification server is not security-sensitive. It does not
41 talk to the network, and it does not talk to local users. The verify
42 server can run chrooted at fixed low privilege.
43 The address verification server can be coerced to store unlimited
45 amounts of garbage. Limiting the cache expiry time trades one problem
46 (disk space exhaustion) for another one (poor response time to client
47 requests).
48 With Postfix version 2.5 and later, the verify(8) server no longer uses
50 root privileges when opening the address_verify_map cache file. The
51 file should now be stored under the Postfix-owned data_directory. As a
52 migration aid, an attempt to open a cache file under a non-Postfix
53 directory is redirected to the Postfix-owned data_directory, and a
54 warning is logged.
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57 Problems and transactions are logged to syslogd(8).
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60 Address verification probe messages add additional traffic to the mail
61 queue. Recipient verification may cause an increased load on down-
62 stream servers in the case of a dictionary attack or a flood of
63 backscatter bounces. Sender address verification may cause your site
64 to be blacklisted by some providers.
65 If the persistent database ever gets corrupted then the world comes to
67 an end and human intervention is needed. This violates a basic Postfix
68 principle.
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71 Changes to main.cf are not picked up automatically, as verify(8) pro‐
72 cesses are long-lived. Use the command "postfix reload" after a config‐
73 uration change.
74 The text below provides only a parameter summary. See postconf(5) for
76 more details including examples.
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79 address_verify_map (see 'postconf -d' output)
80 Lookup table for persistent address verification status storage.
81 address_verify_sender ($double_bounce_sender)
83 The sender address to use in address verification probes; prior
84 to Postfix 2.5 the default was "postmaster".
85 address_verify_positive_expire_time (31d)
87 The time after which a successful probe expires from the address
88 verification cache.
89 address_verify_positive_refresh_time (7d)
91 The time after which a successful address verification probe
92 needs to be refreshed.
93 address_verify_negative_cache (yes)
95 Enable caching of failed address verification probe results.
96 address_verify_negative_expire_time (3d)
98 The time after which a failed probe expires from the address
99 verification cache.
100 address_verify_negative_refresh_time (3h)
102 The time after which a failed address verification probe needs
103 to be refreshed.
104 Available with Postfix 2.7 and later:
106 address_verify_cache_cleanup_interval (12h)
108 The amount of time between verify(8) address verification data‐
109 base cleanup runs.
110
112 By default, probe messages are delivered via the same route as regular
113 messages. The following parameters can be used to override specific
114 message routing mechanisms.
115 address_verify_relayhost ($relayhost)
117 Overrides the relayhost parameter setting for address verifica‐
118 tion probes.
119 address_verify_transport_maps ($transport_maps)
121 Overrides the transport_maps parameter setting for address veri‐
122 fication probes.
123 address_verify_local_transport ($local_transport)
125 Overrides the local_transport parameter setting for address ver‐
126 ification probes.
127 address_verify_virtual_transport ($virtual_transport)
129 Overrides the virtual_transport parameter setting for address
130 verification probes.
131 address_verify_relay_transport ($relay_transport)
133 Overrides the relay_transport parameter setting for address ver‐
134 ification probes.
135 address_verify_default_transport ($default_transport)
137 Overrides the default_transport parameter setting for address
138 verification probes.
139 Available in Postfix 2.3 and later:
141 address_verify_sender_dependent_relayhost_maps ($sender_depen‐
143 dent_relayhost_maps)
144 Overrides the sender_dependent_relayhost_maps parameter setting
145 for address verification probes.
146 Available in Postfix 2.7 and later:
148 address_verify_sender_dependent_default_transport_maps ($sender_depen‐
150 dent_default_transport_maps)
151 Overrides the sender_dependent_default_transport_maps parameter
152 setting for address verification probes.
153
155 config_directory (see 'postconf -d' output)
156 The default location of the Postfix main.cf and master.cf con‐
157 figuration files.
158 daemon_timeout (18000s)
160 How much time a Postfix daemon process may take to handle a
161 request before it is terminated by a built-in watchdog timer.
162 ipc_timeout (3600s)
164 The time limit for sending or receiving information over an
165 internal communication channel.
166 process_id (read-only)
168 The process ID of a Postfix command or daemon process.
169 process_name (read-only)
171 The process name of a Postfix command or daemon process.
172 queue_directory (see 'postconf -d' output)
174 The location of the Postfix top-level queue directory.
175 syslog_facility (mail)
177 The syslog facility of Postfix logging.
178 syslog_name (see 'postconf -d' output)
180 The mail system name that is prepended to the process name in
181 syslog records, so that "smtpd" becomes, for example, "post‐
182 fix/smtpd".
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185 smtpd(8), Postfix SMTP server
186 cleanup(8), enqueue Postfix message
187 postconf(5), configuration parameters
188 syslogd(5), system logging
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191 Use "postconf readme_directory" or "postconf html_directory" to locate
192 this information.
193 ADDRESS_VERIFICATION_README, address verification howto
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196 The Secure Mailer license must be distributed with this software.
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199 This service was introduced with Postfix version 2.1.
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202 Wietse Venema
203 IBM T.J. Watson Research
204 P.O. Box 704
205 Yorktown Heights, NY 10598, USA
206 VERIFY(8)