Milter-before is a Perl script that prevents spam back-scatter. It is a small and efficient tool designed to filter unwanted emails from reaching the inbox.
A few years back in 200?, I was seeking a milter plugin that could prevent our front SMTP relay from accepting mail for invalid user addresses on internal servers. While mails can always be accepted, trying to deliver them to internal SMTP servers results in refusal. The next step is to send them back to their senders, which is typically a bad or faked address. This common issue is referred to as "spam back-scatter", which causes undesirable bounces. Unfortunately, I discovered that the only available implementations were not free, which left me with no other option but to wait.
In October 2007, I began working on a free Perl script to solve the problem. The beta version of the milter-before software is based on some mimedefang code, MLDBM, and Sendmail::Milter. Based on our experience, it runs smoothly for several days without any problems on our front SMTP server. Note that its job is reduced since we run the milter-greylist first. If you are looking for a reliable software to prevent spam back-scatter and bounces at no cost, the milter-before software is an excellent choice.
Version 0.1: N/A