Prefix WhoIs Milter


The Prefix WhoIs Milter is a mail filter for Postfix and Sendmail.  It queries
Prefix WhoIs (whois.pwhois.org by default) about the originating IP address
found in the final Received or X-Originating-IP mail header.  The information
that it returns may be used for greylisting and can be displayed in modern
e-mail clients to provide some background as to the origin of the message.

The Prefix WhoIs milter appends e-mail headers of the form X-PWhois-Field-Name
corresponding to a field in the response from Prefix WhoIs.  Currently, it
inserts information from the Origin-AS, AS-Org-Name, Org-Name, Net-Name, Region,
Country and Country-Code Prefix WhoIs response fields.

The PWhoIs Milter turns boring e-mail headers like this:

To: "You" <you@example.com>
From: "John Doe" <johndoe@example.com>

... into useful message headers like this:

To: "You" <you@example.com>
From: "John Doe" <johndoe@example.com>
X-PWhois-Origin: 4.2.2.1
X-PWhois-Origin-AS: 3356
X-PWhois-AS-Org-Name: Level 3 Communications
X-PWhois-Org-Name: Level 3 Communications, Inc.
X-PWhois-Net-Name: LVLT-ORG-4-8
X-PWhois-City: BROOMFIELD
X-PWhois-Region: COLORADO
X-PWhois-Country: UNITED STATES
X-PWhois-Country-Code: US

The Prefix WhoIs milter implements a safety timeout in case of a network or
Prefix WhoIs outage; if the timeout period elapses, the message passes through
unaltered and without further delay, so it is safe to run even in high-volume
e-mail environments.


Installation Instructions

Libmilter is required to build pwhois-milter.  This is often available in
package repositories, such as libmilter-dev for Debian, or you may wish to use
libmilter from the Sendmail source distribution.  Then, simply issue

# make && make install

and copy the init script corresponding to your system to the proper location.


Usage Hints and Tips

Add to your Postfix main.cf smtpd_milters chain:

inet:localhost:8472

If you have existing milters in your Postfix milter chain, separate them with a
comma or space.  Neither Postfix nor Sendmail will start pwhois-milter for you
so you must run the appropriate init script for your system.  Alternatively, you
may wish to run the milter manually:

pwhois-milter -i /path/to/pidfile.pid -l /path/to/logfile.log [ -u UID -g GID ]

View further command line options by running pwhois-milter with no parameters.

Although pwhois-milter has not been tested with Sendmail, it ought to work if
you add the following to your sendmail.mc:

INPUT_MAIL_FILTER(`PWhois Milter', `S=inet:8472@localhost, T=E:10s')

Signal pwhois-milter with SIGUSR1 to reopen the log file for rotating logs.
(SIGHUP will terminate the milter.)  Preferably configure logrotate(8) or
touch(1) the log file to create it before instructing pwhois-milter to use it.
It may not be able to create the file on its own since it should be running with
limited privileges.