external/ibm-public/postfix/dist/html/verify.8.html

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   7 VERIFY(8)                                                            VERIFY(8)
   8
   9 <b>NAME</b>
  10        verify - Postfix address verification server
  11
  12 <b>SYNOPSIS</b>
  13        <b>verify</b> [generic Postfix daemon options]
  14
  15 <b>DESCRIPTION</b>
  16        The  <a href="verify.8.html"><b>verify</b>(8)</a>  address  verification  server  maintains a
  17        record of what recipient addresses are known to be  deliv-
  18        erable or undeliverable.
  19
  20        Addresses  are  verified  by injecting probe messages into
  21        the Postfix queue. Probe messages are run through all  the
  22        routing and rewriting machinery except for final delivery,
  23        and are discarded rather than being deferred or bounced.
  24
  25        Address verification relies on the answer from the nearest
  26        MTA  for  the  specified  address,  and will therefore not
  27        detect all undeliverable addresses.
  28
  29        The <a href="verify.8.html"><b>verify</b>(8)</a> server is designed to run under  control  by
  30        the  Postfix  master server. It maintains an optional per-
  31        sistent database.  To avoid being interrupted by  "postfix
  32        stop" in the middle of a database update, the process runs
  33        in a separate process group.
  34
  35        The <a href="verify.8.html"><b>verify</b>(8)</a> server implements the following requests:
  36
  37        <b>update</b> <i>address status text</i>
  38               Update  the  status  and  text  of  the   specified
  39               address.
  40
  41        <b>query</b> <i>address</i>
  42               Look  up  the  <i>status</i>  and  <i>text</i>  for the specified
  43               address.  If the status is unknown, a probe is sent
  44               and an "in progress" status is returned.
  45
  46 <b>SECURITY</b>
  47        The address verification server is not security-sensitive.
  48        It does not talk to the network, and it does not  talk  to
  49        local  users.  The verify server can run chrooted at fixed
  50        low privilege.
  51
  52        The address verification server can be  coerced  to  store
  53        unlimited  amounts  of  garbage.  Limiting  the cache size
  54        trades one problem (disk space exhaustion) for another one
  55        (poor response time to client requests).
  56
  57        With  Postfix  version 2.5 and later, the <a href="verify.8.html"><b>verify</b>(8)</a> server
  58        no  longer  uses  root   privileges   when   opening   the
  59        <b><a href="postconf.5.html#address_verify_map">address_verify_map</a></b>  cache  file.  The  file  should now be
  60        stored  under  the  Postfix-owned  <b><a href="postconf.5.html#data_directory">data_directory</a></b>.   As  a
  61        migration  aid,  an  attempt  to open a cache file under a
  62        non-Postfix directory is redirected to  the  Postfix-owned
  63        <b><a href="postconf.5.html#data_directory">data_directory</a></b>, and a warning is logged.
  64
  65 <b>DIAGNOSTICS</b>
  66        Problems and transactions are logged to <b>syslogd</b>(8).
  67
  68 <b>BUGS</b>
  69        The  address  verification  service  is  suitable only for
  70        sites that handle a low mail volume.  Verification  probes
  71        add  additional  traffic  to  the  mail  queue and perform
  72        poorly under high load.  Servers may blacklist sites  that
  73        probe excessively, or that probe excessively for non-exis-
  74        tent recipient addresses.
  75
  76        If the persistent database ever gets  corrupted  then  the
  77        world  comes  to  an end and human intervention is needed.
  78        This violates a basic Postfix principle.
  79
  80 <b>CONFIGURATION PARAMETERS</b>
  81        Changes to <a href="postconf.5.html"><b>main.cf</b></a> are not  picked  up  automatically,  as
  82        <a href="verify.8.html"><b>verify</b>(8)</a> processes are persistent. Use the command "<b>post-</b>
  83        <b>fix reload</b>" after a configuration change.
  84
  85        The text below provides  only  a  parameter  summary.  See
  86        <a href="postconf.5.html"><b>postconf</b>(5)</a> for more details including examples.
  87
  88 <b>CACHE CONTROLS</b>
  89        <b><a href="postconf.5.html#address_verify_map">address_verify_map</a> (empty)</b>
  90               Optional  lookup table for persistent address veri-
  91               fication status storage.
  92
  93        <b><a href="postconf.5.html#address_verify_sender">address_verify_sender</a> ($<a href="postconf.5.html#double_bounce_sender">double_bounce_sender</a>)</b>
  94               The sender address to use in  address  verification
  95               probes; prior to Postfix 2.5 the default was "post-
  96               master".
  97
  98        <b><a href="postconf.5.html#address_verify_positive_expire_time">address_verify_positive_expire_time</a> (31d)</b>
  99               The time after which  a  successful  probe  expires
 100               from the address verification cache.
 101
 102        <b><a href="postconf.5.html#address_verify_positive_refresh_time">address_verify_positive_refresh_time</a> (7d)</b>
 103               The time after which a successful address verifica-
 104               tion probe needs to be refreshed.
 105
 106        <b><a href="postconf.5.html#address_verify_negative_cache">address_verify_negative_cache</a> (yes)</b>
 107               Enable caching of failed address verification probe
 108               results.
 109
 110        <b><a href="postconf.5.html#address_verify_negative_expire_time">address_verify_negative_expire_time</a> (3d)</b>
 111               The  time  after  which a failed probe expires from
 112               the address verification cache.
 113
 114        <b><a href="postconf.5.html#address_verify_negative_refresh_time">address_verify_negative_refresh_time</a> (3h)</b>
 115               The time after which a failed address  verification
 116               probe needs to be refreshed.
 117
 118 <b>PROBE MESSAGE ROUTING CONTROLS</b>
 119        By  default,  probe  messages  are  delivered via the same
 120        route as regular messages.  The following  parameters  can
 121        be used to override specific message routing mechanisms.
 122
 123        <b><a href="postconf.5.html#address_verify_relayhost">address_verify_relayhost</a> ($<a href="postconf.5.html#relayhost">relayhost</a>)</b>
 124               Overrides   the  <a href="postconf.5.html#relayhost">relayhost</a>  parameter  setting  for
 125               address verification probes.
 126
 127        <b><a href="postconf.5.html#address_verify_transport_maps">address_verify_transport_maps</a> ($<a href="postconf.5.html#transport_maps">transport_maps</a>)</b>
 128               Overrides the <a href="postconf.5.html#transport_maps">transport_maps</a> parameter setting  for
 129               address verification probes.
 130
 131        <b><a href="postconf.5.html#address_verify_local_transport">address_verify_local_transport</a> ($<a href="postconf.5.html#local_transport">local_transport</a>)</b>
 132               Overrides the <a href="postconf.5.html#local_transport">local_transport</a> parameter setting for
 133               address verification probes.
 134
 135        <b><a href="postconf.5.html#address_verify_virtual_transport">address_verify_virtual_transport</a> ($<a href="postconf.5.html#virtual_transport">virtual_transport</a>)</b>
 136               Overrides the <a href="postconf.5.html#virtual_transport">virtual_transport</a>  parameter  setting
 137               for address verification probes.
 138
 139        <b><a href="postconf.5.html#address_verify_relay_transport">address_verify_relay_transport</a> ($<a href="postconf.5.html#relay_transport">relay_transport</a>)</b>
 140               Overrides the <a href="postconf.5.html#relay_transport">relay_transport</a> parameter setting for
 141               address verification probes.
 142
 143        <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>
 144               Overrides the <a href="postconf.5.html#default_transport">default_transport</a>  parameter  setting
 145               for address verification probes.
 146
 147 <b>MISCELLANEOUS CONTROLS</b>
 148        <b><a href="postconf.5.html#config_directory">config_directory</a> (see 'postconf -d' output)</b>
 149               The  default  location  of  the Postfix <a href="postconf.5.html">main.cf</a> and
 150               <a href="master.5.html">master.cf</a> configuration files.
 151
 152        <b><a href="postconf.5.html#daemon_timeout">daemon_timeout</a> (18000s)</b>
 153               How much time a Postfix daemon process may take  to
 154               handle  a  request  before  it  is  terminated by a
 155               built-in watchdog timer.
 156
 157        <b><a href="postconf.5.html#ipc_timeout">ipc_timeout</a> (3600s)</b>
 158               The time limit for sending or receiving information
 159               over an internal communication channel.
 160
 161        <b><a href="postconf.5.html#process_id">process_id</a> (read-only)</b>
 162               The  process  ID  of  a  Postfix  command or daemon
 163               process.
 164
 165        <b><a href="postconf.5.html#process_name">process_name</a> (read-only)</b>
 166               The process name of a  Postfix  command  or  daemon
 167               process.
 168
 169        <b><a href="postconf.5.html#queue_directory">queue_directory</a> (see 'postconf -d' output)</b>
 170               The  location of the Postfix top-level queue direc-
 171               tory.
 172
 173        <b><a href="postconf.5.html#syslog_facility">syslog_facility</a> (mail)</b>
 174               The syslog facility of Postfix logging.
 175
 176        <b><a href="postconf.5.html#syslog_name">syslog_name</a> (see 'postconf -d' output)</b>
 177               The mail system  name  that  is  prepended  to  the
 178               process  name  in  syslog  records, so that "smtpd"
 179               becomes, for example, "postfix/smtpd".
 180
 181 <b>SEE ALSO</b>
 182        <a href="smtpd.8.html">smtpd(8)</a>, Postfix SMTP server
 183        <a href="cleanup.8.html">cleanup(8)</a>, enqueue Postfix message
 184        <a href="postconf.5.html">postconf(5)</a>, configuration parameters
 185        syslogd(5), system logging
 186
 187 <b>README FILES</b>
 188        <a href="ADDRESS_VERIFICATION_README.html">ADDRESS_VERIFICATION_README</a>, address verification howto
 189
 190 <b>LICENSE</b>
 191        The  Secure  Mailer  license must be distributed with this
 192        software.
 193
 194 <b>HISTORY</b>
 195        This service was introduced with Postfix version 2.1.
 196
 197 <b>AUTHOR(S)</b>
 198        Wietse Venema
 199        IBM T.J. Watson Research
 200        P.O. Box 704
 201        Yorktown Heights, NY 10598, USA
 202
 203                                                                      VERIFY(8)
 204 </pre> </body> </html>