If you’re running you’re own mail server and looking for an anti-spam solution be sure to take a closer look at ASSP (which stands for AntiSpam SMTP Proxy). I’m using it with my own mail servers and what can I say – I’m more than happy with it.

The pros:

• It’s free, so no risk to try it whatsoever
• It uses a plethora of different spam recognition and fighting techniques, such as:
  • Greylisting (which alone already keeps off 80% and more of unwanted mass mail)
  • Bayesian filter
  • Sender/HELO validation
  • DNS/address blacklisting
  • Sender Policy Framework (SPF) / Sender Rewriting Scheme (SRS)
  • …
• It’s low on CPU use
• Choice between test mode (e.g. tag subject of possible spam with something like [SPAM]) or “real” mode (block spam altogether)
• Lots of options and statistics, all accessible through a browser interface

There are some minor cons, though

• Installation not trivial
• Memory use is not spectacularly low (about 50MB on a machine receiving 1000-2000 mails per day)

I don’t find those issues to be real problems. Once it is installed it runs fine and my servers are able to handle the additional memory use.

Here’s what you need:

• A mail server up and running (e.g. for Windows: hMailServer or MailEnable)
• A working Perl installation(e.g. ActivePerl)
• The modules/3rd party apps which ASSP (optionally) uses – just download “All Perl Modules” from the ASSP sourceforge files, which is a really convenient installer for all the dependencies of ASSP.
• Of course, ASSP itself, for example version 1.4.3.1

Conclusion

For me ASSP has cut down the amount of spam tremendously! I’m running in test mode for two month now. Currently I receive between 0 and 7 mails per day tagged as [SPAM], the rest is blocked by greylisting already.

Some useful links regarding ASSP:

• project page
• users mailing list
• forum
• wiki