The ongoing war against spam.
Since I put postoffice on pell, I've been logging some of the more interesting statistics it's been gathering (how many wrong numbers, how many machines in the blacklist, and how many viruses.) I've finally written scripts to chart all of this:
I get a small but steady stream of viruses, and I used to get dictionary probes up the wazoo before I started blocking MAIL FROM:<> (yes, this violates rfc822, but I never get valid mail from <> and I used to get in the ballpark of 400 dictionary attacks a day.)
Note the steadily increasing number of banned connection attempts; these are primarily attempts to deliver mail from dialup IPs (which I refuse; most ISPs have their own mail servers which I will accept mail from) and I can only guess that there are more and more spammers using virus-infested computers as spam relay hosts as their regular connections are traced and shut down. (This would qualify as "spammers are scum", but it's not too hard to find proof of that these days.)
Update: On the 20th, I started refusing mail from sites that don't have properly configured reverse DNS. I'm doing soft bounces (4xx instead of 5xx) to give the site owners a chance to correct their DNS and get their spam into pell, so as a result I'm now seeing a whole lot of sites that get the 4xx and go into a crazed frenzy of hammering against postoffice until they get bunged into the firewall deny list. There appear to be quite a few sites out there that just don't want to take come back later for an answer (joining the proud ranks of sites that go apeshit if the door is answered by someone who doesn't look exactly like sendmail), but which feel that if they batter really hard at the door then I'll give in and let them deliver their rotting bundles of spam and windows viruses.