As I do my own hosting the problem of spam has been something that comes up a lot. I use Scalix so there wasn’t much instantly available when I first looked. A lot of the open source guides tell you about anti-spam measures for Postfix, Qmail and such like. However, I did come across ASSP which is a pretty nifty package. It’s easy to install as it’s just a proxy for your mail server. With Scalix, sendmail is used so I just set that to listen on a different port and then ASSP will proxy connections on port 25. Its anti-spam measures are pretty aggressive so you would probably want to spend some time understanding how it’s going to affect you and monitor quite closely. However, it has really cut down my spam massively so it’s well worth investigating if you want something that will sit in front of an existing mail setup.
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