SpamAssassin really sucks. Yes, I’ve heard you have to tweak the Bayes filtering it uses. You might even use graylisting to try to prevent some spam. And you might even install Pyzor, Razor and DCC on your server, which can help. But chances are it still might not be enough. Lowering the spam score threshold (points) in SpamAssassin is a bad idea as it will increase the false positives (good email that will get marked as spam). Even using blacklists such as:
resulted in not cutting down on spam enough (I found zen.spamhaus.org to block too many valid emails).
Well let me introduce you to ASSP (Anti-Spam STMP Proxy). It’s kind of complicated to install and configure, but it works very well. It uses multiple methods to block spam:
- Multiple Weighted DNSBLs
- Multiple Weighted URIBLs
- Weighted Regular Expression Filtering
- Penalty Box
- Attachment Blocking
- ClamAV and FileScan
- Blocking Reporting
- LDAP support
- Backscatter Detection
However, the best things I find about it is the web interface for configuration and the email interface. The web interface can be overwhelming because of the tons of options in there, but you can add in a whitelist of domains and specific email addresses. You can also tweak the keywords or phrases to denote spam. Any emails sent from your “local domains” have the “to” (recipient address) added automatically to your whitelist. Anyway, try it out if you have tons of spam coming in. Check out the wiki for some tips on setting it up.