Email Filters and Utilities
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I've written some email filtering software and utilities that may make
your life easier in controlling the flood of spam and viruses that
blight your inbox. They are listed below.
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A powerful spam filter which I use
for blocking spam as well as general email management (such as sorting
incoming email into different folders so that high-traffic email lists
don't flood my normal inbox). This filter was originally written by
Lars Wirzenius, but I've heavily modified it. The basic method used in
this filter to combat spam is to bounce messages from people I don't
know, requiring them to resend their message with a password (the
bounce message tells them the password). This is a personal filter,
not a system-wide filter.
-
milter-dnsrbl, a sendmail
milter which allows an email administrator to reject messages which
originate from, or are relayed via, an MTA which is listed in a
DNS Real-time Black List (DNSRBL). Features include:
- reject a message with a 44x (temporary) error
- reject a message with a 55x (permanent) error
- discard a message (silently)
- accept a message, but insert a tag (header line)
- stall the connection indefinately (until sender times out)
- stall the connection for a specified time
- check Received: header lines for IP addresses of previous relay
machines
- wildcard matches of A record values
It is currently packaged as part of my
email utilities.
-
milter-regexp, a sendmail
milter which allows an email administrator to reject messages based on
regular expression matches. Features include:
- reject a message with a 44x (temporary) error
- reject a message with a 55x (permanent) error
- discard a message (silently)
- accept a message, but insert a tag (header line)
- redirect the message to a different destination
- accept the message with no changes
- stall the connection for a specified time
- support for per-recipient configuration files (at the discretion
of the system administrator)
It is currently packaged as part of my
email utilities.
-
milter-size, a sendmail
milter which allows an email administrator to reject messages
of a specified size range. It is currently packaged as part of my
email utilities. It also can send message sizes over a UDP
socket, which can be used for later analysis or real-time display
(such as a histogram of sizes).