257 lines
8.2 KiB
Groff
257 lines
8.2 KiB
Groff
.TH VERIFY 8
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.ad
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.fi
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.SH NAME
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verify
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\-
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Postfix address verification server
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.SH "SYNOPSIS"
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.nf
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\fBverify\fR [generic Postfix daemon options]
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.SH DESCRIPTION
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.ad
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.fi
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The \fBverify\fR(8) address verification server maintains a record
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of what recipient addresses are known to be deliverable or
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undeliverable.
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Addresses are verified by injecting probe messages into the
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Postfix queue. Probe messages are run through all the routing
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and rewriting machinery except for final delivery, and are
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discarded rather than being deferred or bounced.
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Address verification relies on the answer from the nearest
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MTA for the specified address, and will therefore not detect
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all undeliverable addresses.
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The \fBverify\fR(8) server is designed to run under control
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by the Postfix
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master server. It maintains an optional persistent database.
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To avoid being interrupted by "postfix stop" in the middle
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of a database update, the process runs in a separate process
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group.
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The \fBverify\fR(8) server implements the following requests:
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.IP "\fBupdate\fI address status text\fR"
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Update the status and text of the specified address.
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.IP "\fBquery\fI address\fR"
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Look up the \fIstatus\fR and \fItext\fR for the specified
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\fIaddress\fR.
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If the status is unknown, a probe is sent and an "in progress"
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status is returned.
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.SH "SECURITY"
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.na
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.nf
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.ad
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.fi
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The address verification server is not security\-sensitive. It does
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not talk to the network, and it does not talk to local users.
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The verify server can run chrooted at fixed low privilege.
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The address verification server can be coerced to store
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unlimited amounts of garbage. Limiting the cache expiry
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time
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trades one problem (disk space exhaustion) for another
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one (poor response time to client requests).
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With Postfix version 2.5 and later, the \fBverify\fR(8)
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server no longer uses root privileges when opening the
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\fBaddress_verify_map\fR cache file. The file should now
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be stored under the Postfix\-owned \fBdata_directory\fR. As
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a migration aid, an attempt to open a cache file under a
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non\-Postfix directory is redirected to the Postfix\-owned
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\fBdata_directory\fR, and a warning is logged.
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.SH DIAGNOSTICS
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.ad
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.fi
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Problems and transactions are logged to \fBsyslogd\fR(8)
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or \fBpostlogd\fR(8).
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.SH BUGS
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.ad
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.fi
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Address verification probe messages add additional traffic
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to the mail queue.
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Recipient verification may cause an increased load on
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down\-stream servers in the case of a dictionary attack or
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a flood of backscatter bounces.
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Sender address verification may cause your site to be
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denylisted by some providers.
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If the persistent database ever gets corrupted then the world
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comes to an end and human intervention is needed. This violates
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a basic Postfix principle.
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.SH "CONFIGURATION PARAMETERS"
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.nf
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.ad
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.fi
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Changes to \fBmain.cf\fR are not picked up automatically,
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as \fBverify\fR(8)
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processes are long\-lived. Use the command "\fBpostfix reload\fR" after
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a configuration change.
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The text below provides only a parameter summary. See
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\fBpostconf\fR(5) for more details including examples.
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.SH "PROBE MESSAGE CONTROLS"
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.nf
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.ad
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.IP "\fBaddress_verify_sender ($double_bounce_sender)\fR"
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The sender address to use in address verification probes; prior
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to Postfix 2.5 the default was "postmaster".
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.PP
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Available with Postfix 2.9 and later:
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.IP "\fBaddress_verify_sender_ttl (0s)\fR"
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The time between changes in the time\-dependent portion of address
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verification probe sender addresses.
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.SH "CACHE CONTROLS"
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.na
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.nf
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.ad
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.fi
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.IP "\fBaddress_verify_map (see 'postconf -d' output)\fR"
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Lookup table for persistent address verification status
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storage.
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.IP "\fBaddress_verify_positive_expire_time (31d)\fR"
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The time after which a successful probe expires from the address
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verification cache.
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.IP "\fBaddress_verify_positive_refresh_time (7d)\fR"
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The time after which a successful address verification probe needs
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to be refreshed.
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.IP "\fBaddress_verify_negative_cache (yes)\fR"
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Enable caching of failed address verification probe results.
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.IP "\fBaddress_verify_negative_expire_time (3d)\fR"
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The time after which a failed probe expires from the address
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verification cache.
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.IP "\fBaddress_verify_negative_refresh_time (3h)\fR"
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The time after which a failed address verification probe needs to
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be refreshed.
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.PP
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Available with Postfix 2.7 and later:
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.IP "\fBaddress_verify_cache_cleanup_interval (12h)\fR"
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The amount of time between \fBverify\fR(8) address verification
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database cleanup runs.
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.SH "PROBE MESSAGE ROUTING CONTROLS"
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.nf
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.ad
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.fi
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By default, probe messages are delivered via the same route
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as regular messages. The following parameters can be used to
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override specific message routing mechanisms.
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.IP "\fBaddress_verify_relayhost ($relayhost)\fR"
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Overrides the relayhost parameter setting for address verification
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probes.
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.IP "\fBaddress_verify_transport_maps ($transport_maps)\fR"
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Overrides the transport_maps parameter setting for address verification
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probes.
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.IP "\fBaddress_verify_local_transport ($local_transport)\fR"
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Overrides the local_transport parameter setting for address
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verification probes.
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.IP "\fBaddress_verify_virtual_transport ($virtual_transport)\fR"
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Overrides the virtual_transport parameter setting for address
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verification probes.
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.IP "\fBaddress_verify_relay_transport ($relay_transport)\fR"
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Overrides the relay_transport parameter setting for address
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verification probes.
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.IP "\fBaddress_verify_default_transport ($default_transport)\fR"
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Overrides the default_transport parameter setting for address
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verification probes.
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.PP
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Available in Postfix 2.3 and later:
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.IP "\fBaddress_verify_sender_dependent_relayhost_maps ($sender_dependent_relayhost_maps)\fR"
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Overrides the sender_dependent_relayhost_maps parameter setting for address
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verification probes.
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.PP
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Available in Postfix 2.7 and later:
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.IP "\fBaddress_verify_sender_dependent_default_transport_maps ($sender_dependent_default_transport_maps)\fR"
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Overrides the sender_dependent_default_transport_maps parameter
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setting for address verification probes.
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.SH "SMTPUTF8 CONTROLS"
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.nf
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.ad
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.fi
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Preliminary SMTPUTF8 support is introduced with Postfix 3.0.
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.IP "\fBsmtputf8_autodetect_classes (sendmail, verify)\fR"
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Detect that a message requires SMTPUTF8 support for the specified
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mail origin classes.
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.PP
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Available in Postfix version 3.2 and later:
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.IP "\fBenable_idna2003_compatibility (no)\fR"
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Enable 'transitional' compatibility between IDNA2003 and IDNA2008,
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when converting UTF\-8 domain names to/from the ASCII form that is
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used for DNS lookups.
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.SH "MISCELLANEOUS CONTROLS"
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.IP "\fBconfig_directory (see 'postconf -d' output)\fR"
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The default location of the Postfix main.cf and master.cf
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configuration files.
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.IP "\fBdaemon_timeout (18000s)\fR"
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How much time a Postfix daemon process may take to handle a
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request before it is terminated by a built\-in watchdog timer.
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.IP "\fBipc_timeout (3600s)\fR"
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The time limit for sending or receiving information over an internal
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communication channel.
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.IP "\fBprocess_id (read\-only)\fR"
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The process ID of a Postfix command or daemon process.
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.IP "\fBprocess_name (read\-only)\fR"
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The process name of a Postfix command or daemon process.
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.IP "\fBqueue_directory (see 'postconf -d' output)\fR"
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The location of the Postfix top\-level queue directory.
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.IP "\fBsyslog_facility (mail)\fR"
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The syslog facility of Postfix logging.
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.IP "\fBsyslog_name (see 'postconf -d' output)\fR"
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A prefix that is prepended to the process name in syslog
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records, so that, for example, "smtpd" becomes "prefix/smtpd".
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.PP
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Available in Postfix 3.3 and later:
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.IP "\fBservice_name (read\-only)\fR"
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The master.cf service name of a Postfix daemon process.
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.SH "SEE ALSO"
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.nf
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smtpd(8), Postfix SMTP server
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cleanup(8), enqueue Postfix message
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postconf(5), configuration parameters
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postlogd(8), Postfix logging
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syslogd(8), system logging
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.SH "README FILES"
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.nf
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.ad
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.fi
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Use "\fBpostconf readme_directory\fR" or
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"\fBpostconf html_directory\fR" to locate this information.
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ADDRESS_VERIFICATION_README, address verification howto
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.SH "LICENSE"
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.nf
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.ad
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.fi
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The Secure Mailer license must be distributed with this software.
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.SH HISTORY
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.ad
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.fi
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.ad
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.fi
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This service was introduced with Postfix version 2.1.
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.SH "AUTHOR(S)"
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.nf
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Wietse Venema
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IBM T.J. Watson Research
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P.O. Box 704
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Yorktown Heights, NY 10598, USA
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Wietse Venema
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Google, Inc.
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111 8th Avenue
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New York, NY 10011, USA
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