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       pop-before-smtp - watch log for POP/IMAP auth, update map allowing SMTP


        nohup pop-before-smtp [--config=FILE] [--[no]write] [--[no]debug] \
            [--[no]flock] [--reprocess] [--watchlog=FILE] [--dbfile=FILE] \
            [--logto=FILE] [--grace=SECONDS] [--daemon=PIDFILE] \
            [--version] [--dumpconfig] [--list]


       pop-before-smtp watches your mail log file (e.g. /var/log/mail.log) for
       lines written by your POP/IMAP software (e.g. UW popd/imapd) that
       indicate a successful login. When found, pop-before-smtp installs an
       entry for the IP in an on-disk hash (DB) that is watched by your SMTP
       software (e.g. Postfix, sendmail, qmail, etc.). It then expires these
       entries when 30 minutes have elapsed after the last POP/IMAP access
       from that IP.


           Specify the config file to read instead of
           /etc/pop-before-smtp/pop-before-smtp.conf.  Useful for testing a
           new configuration before you install it. This option must occur
           first on the command-line since it will be processed before reading
           the config file, and all other options will be processed after
           reading the config file.

           Specify --nowrite if you don’t want the DB file to be even opened,
           let alone updated. Useful for trying out pattern-matching rules,
           especially when used with --debug and --reprocess.  (If your mail-
           log is world-readable, you can even run the test as a non-
           privileged user.)

           If you specify --debug, logging to stdout will be enabled, plus
           extra debug messages will be generated to help you diagnose
           local/remote IP distinctions. Specify --logto after this option if
           you want the messages to go somewhere other than stdout.  Often
           combined with --reprocess.

           Using --noflock will turn off the default file-locking used on the
           DB file.

           Parse the whole mail-log file, pretending that each line is
           happening again.  Useful for testing, especially when combined with
           --debug and possibly --nowrite.

           You can specify what mail-log to watch for POP/IMAP events.  To see
           what the default value is for your system, run "pop-before-smtp

           You can specify what DB file to update.  To see what the default
           value is for your system, run "pop-before-smtp --dumpconfig".
           Typically, the filename that is created/updated is this name with a
           ".db" suffix added (because the default tie function appends the
           ".db" onto the specified db name -- if you supply a custom tie
           function, it is free to choose to do something else).

           Turns on logging to the specified file (use "-" for stdout).

           Set the number of seconds that an IP address is authorized after it
           successfully signs in via POP or IMAP.

           Output the current version of the script and exit.  May be combined
           with --dumpconfig and --list in the same run.

           Output some config info and exit. This makes it easy to see what
           things like the dbfile, logto, and watchlog values are being set to
           in the config file.  May be combined with --version and --list in
           the same run.

           List the current IPs contained in the DB file (if any) and exit.
           May be combined with --version and --dumpconfig in the same run.

           Become a daemon by forking, redirecting STDIN/STDOUT/STDERR to
           /dev/null, calling setsid, calling chdir(’/’), and writing out the
           process ID of the forked process into the specified PIDFILE.


       This daemon directly requires four modules from CPAN, which are not
       included in the base Perl release as of this writing.  See the
       quickstart guide for more information (either look at the
       README.QUICKSTART file in the source or visit

       You should edit the supplied file to customize
       things for your local system, such as scanning for the right POP/IMAP
       authorization, setting various options, etc.  Again, the quickstart
       guide cover this.

       When starting up, pop-before-smtp builds an internal table of all
       netblocks natively permitted by your SMTP software (for Postfix it
       looks at the output of "postconf mynetworks"). This allows us to filter
       out local IP addresses that are already authorized and thus need no
       special help from us.

       This daemon likes a couple of helpers. Several init scripts are
       included with the source and a version customized for your current OS
       may have been installed in the same package as the pop-before-smtp

       Once pop-before-smtp has been started (and thus the database file has
       been created), you’ll need to modify your MTA’s configuration to read
       the IPs from the database file.  This is also covered in the quickstart


       See the website for the latest
       version.  See the mailing list (referenced on the website) for support.


       pop-before-smtp keeps two data structures for all currently-allowed
       hosts: a queue, and a hash. The queue contains [ipaddr, time] records,
       while the hash contains ipaddr => time. Every time the daemon wakes up
       to deal with something else from the logfile handle, it peeks a the
       front of the queue, and when the timestamp of the record there has
       expired (is > 30 minutes old) it tosses it, and if the timestamp in the
       hash equals the timestamp in the queue, it deletes the hash entry and
       the on-disk db file entry.

       pop-before-smtp protects the writes to the db file by flock.  As far as
       I know, the consequences of a collision (corrupt read in an smtpd) are
       relatively mild, and the likelihood of one is remote, but the
       performance impact of the locking seems to be negligible, so it’s
       enabled by default.  To disable the flocking, invoke with --noflock or
       set "$flock = 0" in the config file.


       Pop-before-smtp was created by Bennett Todd <>.  It is
       currently being maintained by Wayne Davison