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.
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15 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.
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20 Address verification relies on the answer from the nearest MTA for the
21 specified address, and will therefore not detect all undeliverable
22 addresses.
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24 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.
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29 The verify(8) server implements the following requests:
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31 update address status text
32 Update the status and text of the specified address.
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34 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.
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44 The address verification server can be coerced to store unlimited
45 amounts of garbage. Limiting the cache size trades one problem (disk
46 space exhaustion) for another one (poor response time to client
47 requests).
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49 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 The address verification service is suitable only for sites that handle
61 a low mail volume. Verification probes add additional traffic to the
62 mail queue and perform poorly under high load. Servers may blacklist
63 sites that probe excessively, or that probe excessively for non-exis‐
64 tent recipient addresses.
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66 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 persistent. Use the command "postfix reload" after a config‐
73 uration change.
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75 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 (empty)
80 Optional lookup table for persistent address verification status
81 storage.
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83 address_verify_sender ($double_bounce_sender)
84 The sender address to use in address verification probes; prior
85 to Postfix 2.5 the default was "postmaster".
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87 address_verify_positive_expire_time (31d)
88 The time after which a successful probe expires from the address
89 verification cache.
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91 address_verify_positive_refresh_time (7d)
92 The time after which a successful address verification probe
93 needs to be refreshed.
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95 address_verify_negative_cache (yes)
96 Enable caching of failed address verification probe results.
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98 address_verify_negative_expire_time (3d)
99 The time after which a failed probe expires from the address
100 verification cache.
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102 address_verify_negative_refresh_time (3h)
103 The time after which a failed address verification probe needs
104 to be refreshed.
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107 By default, probe messages are delivered via the same route as regular
108 messages. The following parameters can be used to override specific
109 message routing mechanisms.
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111 address_verify_relayhost ($relayhost)
112 Overrides the relayhost parameter setting for address verifica‐
113 tion probes.
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115 address_verify_transport_maps ($transport_maps)
116 Overrides the transport_maps parameter setting for address veri‐
117 fication probes.
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119 address_verify_local_transport ($local_transport)
120 Overrides the local_transport parameter setting for address ver‐
121 ification probes.
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123 address_verify_virtual_transport ($virtual_transport)
124 Overrides the virtual_transport parameter setting for address
125 verification probes.
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127 address_verify_relay_transport ($relay_transport)
128 Overrides the relay_transport parameter setting for address ver‐
129 ification probes.
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131 address_verify_default_transport ($default_transport)
132 Overrides the default_transport parameter setting for address
133 verification probes.
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136 config_directory (see 'postconf -d' output)
137 The default location of the Postfix main.cf and master.cf con‐
138 figuration files.
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140 daemon_timeout (18000s)
141 How much time a Postfix daemon process may take to handle a
142 request before it is terminated by a built-in watchdog timer.
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144 ipc_timeout (3600s)
145 The time limit for sending or receiving information over an
146 internal communication channel.
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148 process_id (read-only)
149 The process ID of a Postfix command or daemon process.
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151 process_name (read-only)
152 The process name of a Postfix command or daemon process.
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154 queue_directory (see 'postconf -d' output)
155 The location of the Postfix top-level queue directory.
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157 syslog_facility (mail)
158 The syslog facility of Postfix logging.
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160 syslog_name (see 'postconf -d' output)
161 The mail system name that is prepended to the process name in
162 syslog records, so that "smtpd" becomes, for example, "post‐
163 fix/smtpd".
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166 smtpd(8), Postfix SMTP server
167 cleanup(8), enqueue Postfix message
168 postconf(5), configuration parameters
169 syslogd(5), system logging
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172 Use "postconf readme_directory" or "postconf html_directory" to locate
173 this information.
174 ADDRESS_VERIFICATION_README, address verification howto
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177 The Secure Mailer license must be distributed with this software.
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180 This service was introduced with Postfix version 2.1.
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183 Wietse Venema
184 IBM T.J. Watson Research
185 P.O. Box 704
186 Yorktown Heights, NY 10598, USA
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190 VERIFY(8)