There are many spam filters available. It is best to define criteria before beginning the evaluation, and consider the overall features of each solution rather than focus on any single factor. Here are some criteria to consider when choosing an additional spam filter:
The degree of integration with procmail or with the MTA in use: If system configuration is complicated, installation will take longer, and consequently upgrades may be difficult.
The load on the host system: This is particularly relevant if the spam filter is run on the same machine as SpamAssassin, or if older hardware is used to pre-filter email.
Underlying technology: Any approach or technology significantly different to SpamAssassin may improve overall detection rates. Any technology that is identical to that used by SpamAssassin, for example, Razor or DCC, may still be used to lower the load on SpamAssassin, by removing emails that fail these tests, and by performing checks that SpamAssassin no...
