NAME
verify
-
Postfix address verification server
SYNOPSIS
vveerriiffyy [generic Postfix daemon options]
DESCRIPTION
The vveerriiffyy(8) address verification server maintains a record
of what recipient addresses are known to be deliverable 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 vveerriiffyy(8) server is designed to run under control
by the Postfix
master server. It maintains an optional persistent database.
To avoid being interrupted by "postfix stop" in the middle
of a database update, the process runs in a separate process
group.
The vveerriiffyy(8) server implements the following requests:
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uuppddaattee _a_d_d_r_e_s_s _s_t_a_t_u_s _t_e_x_t
Update the status and text of the specified address.
-
-
qquueerryy _a_d_d_r_e_s_s
Look up the _s_t_a_t_u_s and _t_e_x_t for the specified
-
_a_d_d_r_e_s_s.
If the status is unknown, a probe is sent and an "in progress"
status is returned.
SECURITY
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 expiry
time
trades one problem (disk space exhaustion) for another
one (poor response time to client requests).
With Postfix version 2.5 and later, the vveerriiffyy(8)
server no longer uses root privileges when opening the
aaddddrreessss__vveerriiffyy__mmaapp cache file. The file should now
be stored under the Postfix-owned ddaattaa__ddiirreeccttoorryy. As
a migration aid, an attempt to open a cache file under a
non-Postfix directory is redirected to the Postfix-owned
ddaattaa__ddiirreeccttoorryy, and a warning is logged.
DIAGNOSTICS
Problems and transactions are logged to ssyyssllooggdd(8).
BUGS
Address verification probe messages add additional traffic
to the mail queue.
Recipient verification may cause an increased load on
down-stream servers in the case of a dictionary attack or
a flood of backscatter bounces.
Sender address verification may cause your site to be
blacklisted by some providers.
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.
CONFIGURATION PARAMETERS
Changes to mmaaiinn..ccff are not picked up automatically,
as vveerriiffyy(8)
processes are long-lived. Use the command "ppoossttffiixx rreellooaadd" after
a configuration change.
The text below provides only a parameter summary. See
ppoossttccoonnff(5) for more details including examples.
CACHE CONTROLS
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aaddddrreessss__vveerriiffyy__mmaapp ((sseeee ''ppoossttccoonnff --dd'' oouuttppuutt))
Lookup table for persistent address verification status
-
storage.
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aaddddrreessss__vveerriiffyy__sseennddeerr (($$ddoouubbllee__bboouunnccee__sseennddeerr))
The sender address to use in address verification probes; prior
-
to Postfix 2.5 the default was "postmaster".
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aaddddrreessss__vveerriiffyy__ppoossiittiivvee__eexxppiirree__ttiimmee ((3311dd))
The time after which a successful probe expires from the address
-
verification cache.
-
aaddddrreessss__vveerriiffyy__ppoossiittiivvee__rreeffrreesshh__ttiimmee ((77dd))
The time after which a successful address verification probe needs
-
to be refreshed.
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aaddddrreessss__vveerriiffyy__nneeggaattiivvee__ccaacchhee ((yyeess))
Enable caching of failed address verification probe results.
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aaddddrreessss__vveerriiffyy__nneeggaattiivvee__eexxppiirree__ttiimmee ((33dd))
The time after which a failed probe expires from the address
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verification cache.
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aaddddrreessss__vveerriiffyy__nneeggaattiivvee__rreeffrreesshh__ttiimmee ((33hh))
The time after which a failed address verification probe needs to
-
be refreshed.
Available with Postfix 2.7 and later:
-
aaddddrreessss__vveerriiffyy__ccaacchhee__cclleeaannuupp__iinntteerrvvaall ((1122hh))
The amount of time between vveerriiffyy(8) address verification
-
database cleanup runs.
PROBE MESSAGE ROUTING CONTROLS
By default, probe messages are delivered via the same route
as regular messages. The following parameters can be used to
override specific message routing mechanisms.
-
aaddddrreessss__vveerriiffyy__rreellaayyhhoosstt (($$rreellaayyhhoosstt))
Overrides the relayhost parameter setting for address verification
-
probes.
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aaddddrreessss__vveerriiffyy__ttrraannssppoorrtt__mmaappss (($$ttrraannssppoorrtt__mmaappss))
Overrides the transport_maps parameter setting for address verification
-
probes.
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aaddddrreessss__vveerriiffyy__llooccaall__ttrraannssppoorrtt (($$llooccaall__ttrraannssppoorrtt))
Overrides the local_transport parameter setting for address
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verification probes.
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aaddddrreessss__vveerriiffyy__vviirrttuuaall__ttrraannssppoorrtt (($$vviirrttuuaall__ttrraannssppoorrtt))
Overrides the virtual_transport parameter setting for address
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verification probes.
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aaddddrreessss__vveerriiffyy__rreellaayy__ttrraannssppoorrtt (($$rreellaayy__ttrraannssppoorrtt))
Overrides the relay_transport parameter setting for address
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verification probes.
-
aaddddrreessss__vveerriiffyy__ddeeffaauulltt__ttrraannssppoorrtt (($$ddeeffaauulltt__ttrraannssppoorrtt))
Overrides the default_transport parameter setting for address
-
verification probes.
Available in Postfix 2.3 and later:
-
aaddddrreessss__vveerriiffyy__sseennddeerr__ddeeppeennddeenntt__rreellaayyhhoosstt__mmaappss (($$sseennddeerr__ddeeppeennddeenntt__rreellaayyhhoosstt__mmaappss))
Overrides the sender_dependent_relayhost_maps parameter setting for address
-
verification probes.
Available in Postfix 2.7 and later:
-
aaddddrreessss__vveerriiffyy__sseennddeerr__ddeeppeennddeenntt__ddeeffaauulltt__ttrraannssppoorrtt__mmaappss (($$sseennddeerr__ddeeppeennddeenntt__ddeeffaauulltt__ttrraannssppoorrtt__mmaappss))
Overrides the sender_dependent_default_transport_maps parameter
-
setting for address verification probes.
MISCELLANEOUS CONTROLS
-
ccoonnffiigg__ddiirreeccttoorryy ((sseeee ''ppoossttccoonnff --dd'' oouuttppuutt))
The default location of the Postfix main.cf and master.cf
-
configuration files.
-
ddaaeemmoonn__ttiimmeeoouutt ((1188000000ss))
How much time a Postfix daemon process may take to handle a
-
request before it is terminated by a built-in watchdog timer.
-
iippcc__ttiimmeeoouutt ((33660000ss))
The time limit for sending or receiving information over an internal
-
communication channel.
-
pprroocceessss__iidd ((rreeaadd--oonnllyy))
The process ID of a Postfix command or daemon process.
-
-
pprroocceessss__nnaammee ((rreeaadd--oonnllyy))
The process name of a Postfix command or daemon process.
-
-
qquueeuuee__ddiirreeccttoorryy ((sseeee ''ppoossttccoonnff --dd'' oouuttppuutt))
The location of the Postfix top-level queue directory.
-
-
ssyysslloogg__ffaacciilliittyy ((mmaaiill))
The syslog facility of Postfix logging.
-
-
ssyysslloogg__nnaammee ((sseeee ''ppoossttccoonnff --dd'' oouuttppuutt))
The mail system name that is prepended to the process name in syslog
-
records, so that "smtpd" becomes, for example, "postfix/smtpd".
SEE ALSO
smtpd(8), Postfix SMTP server
cleanup(8), enqueue Postfix message
postconf(5), configuration parameters
syslogd(5), system logging
README FILES
Use "ppoossttccoonnff rreeaaddmmee__ddiirreeccttoorryy" or
"ppoossttccoonnff hhttmmll__ddiirreeccttoorryy" to locate this information.
ADDRESS_VERIFICATION_README, address verification howto
LICENSE
The Secure Mailer license must be distributed with this software.
HISTORY
This service was introduced with Postfix version 2.1.
AUTHOR(S)
Wietse Venema
IBM T.J. Watson Research
P.O. Box 704
Yorktown Heights, NY 10598, USA