Message for you Sir!

Ubuntu LogoAt last, I’ve settled on a mail configuration that I like, blocks viruses, is fast and has outstanding spam filtering. There’s a few bits to it, but essentially, it works like this:

Mail arrives on port 25 (port forwarded through my firewall) where ASSP is listening. ASSP is, on the surface, a bog standard SMTP proxy, but has extremely clever spam filtering. It does all the usual things – Bayesian / adaptive filtering, DNSRBL lookups, spoof detection, etc, but it also has a very neat grey-listing feature. Basically, what this does is occasionally tells the upstream MTA that it’s too busy and to try again later. Most spam bots will, at this point, move onto the next target – ASSP learns that this is a spammer and will refuse connections from that particular host.  ASSP also runs everything through ClamAV to look for malware, before punting it to the real mail server – postfix – running on a completely different port and only accepting connections from localhost.

Postfix, helpful little chap that it is, delivers mail locally in maildir format, where it’s served up to our hungry email clients via Dovecot‘s IMAP service. Net result of all this, of course, is that it’s quick, it’s lovely and it has nice crap-evading properties.

It’s been a while since mail was as quick as news on our machine (Leafnode FTW, by the way), so it’s good to be able to glance at mail without the disk grinding its way through fifty tons of spam.

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