It can preserve junk messages for later review or delete them. It can track filtering statistics. SalMoN was intended to bring the regular expression matching feature set of filters like procmail to the user community in an easy to use, easy to understand, simple to support mechanism. By running on virtually any UNIX Email hub, SalMoN provides spam protection for UNIX mail users as well as IMAP and POP clients like Netscape and Eudora. SalMoN makes use of several different rules when making its determinations.
Rules based message checking is likely to filter out the overwhelming majority of junk e-mail.
Obviously because spammers can forge a nearly limitless variety of mail headers, this technique and any program that uses it, may eventually meet with limited success. For that reason, SalMoN employs, depending on the command line options used, several additional filtering techniques or heuristics . Rather than go into complete detail regarding SalMoN's use of heuristics to validate e-mail messages, which could potentially compromise its effectiveness in the long run, it's simpler to explain the fundamental premise the filter uses. Virtually all spammers rely on forged e-mail headers. They don't want to incur the wrath of those who receive their junk, the ISPs that may suffer for it, or the sys admins who have to deal with user complaints and bounced mail.