spam.his.com (Barracuda) SPAM filtering philosophy
The Barracuda filters are actually more effective than Postini's but Barracuda has a different philosophy:
Postini was quarantining some amount of non-spam mail, which was a serious problem from our point of view because at best, it resulted in delayed mail, and since many people don't check their quarantines, it resulted in lost mail.
Barracuda's bias is to try to never quarantine non-spam (except from bulk sources), so it does let a little spam through. We think this is an OK tradeoff.
Barracuda is much better at identifying mail from Commercial senders, or from mailing lists that are not spammers and provide an unsubscribe link.
The right way to stop receiving those commercial emails is:
- UNSUBSCRIBE so they stop sending it.
- If that does not work, block them.
Also, Barracuda is much better at keeping the blatant spam that you never want to see out of your quarantine - the idea there is that it's much easier to go through your quarantine if it isn't full of junk from spambots on infected PCs around the world. About 90% of mail is in this category - the stuff that gets through to your inbox and quarantine is the remaining 10% that has some chance of being real mail. This results in less stuff in your quarantine, so when you compare the spam that got through with what's in quarantine it doesn't look as if the Barracuda filters were working very well, when in fact they were working fine.
Another way that Barracuda is better is how quickly they identify new spam techniques - Postini only updated their filters every 24-48 hours so when a blast came through we'd see one or two days of it before it would start getting blocked or quarantined. Barracuda updates their filters every 20 minutes on average, and we rarely see spam blast last longer than 20 minutes before getting blocked.