Spam volumes have been rising continually around here. I started my foray into automated spam filtering a couple of years back; at the time, I was receiving about 100 per _quarter_. Now I’m getting almost 100 per _day_.

I needed an excuse to upgrade my “postfix”: install to the new “2.1 release”:, so I decided to install “postgrey”:, a “greylisting”: daemon. So far I’m using it after all of my other spamtraps, but it seems to be working reasonably well. I’ll be watching the logs for a while to make sure…

In a nutshell, greylisting relies on the fact that spammers use dump-and-run tactics, while legitimate email gets queued at the sender. So, when a new, previously unknown client connects, the mailserver sends a “temporary deny”. If that connection is a spammer, they’ll probably not return; the reject means the spam was refused. If the sender was legitimate, it will retry, and our server will allow the retry through.

Pretty cool, if you ask me :-)

posted at 9:40 pm on Tuesday, July 06, 2004 in Site News | Comments Off on greylist

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