So, I installed SpamAssassin. It's been only a few hours, and I love it already. Unfortunately one of the things I'd hope it would catch, it doesn't--the klez worm and its kindred. I've no complaints about that, though, as it never claimed it did, and what it does it does really well.
Since I still want Klez dead, that means Plan B. In this case, MIMEDefang from Roaring Penguin. That's fine, except it wants Sendmail 8.12.x, while I'm running a RedHat build of 8.11.x. (Which I manage, no less, through the mailconf portion of linuxconf) There are many things I like doing, but rebuilding sendmail is not one of them. Every time I do, something gets screwed up, probably because I insist on using a custom config setup with a tool that hates custom configs. (I keep my mailing list aliases in a separate aliases file, though given how often they change there's little point these days)
Of course, I'm also running a 2.2.something linux kernel, with an older glibc, so I have no doubt that when I go to build the new sendmail I'll find a dozen other upgrades needed, and each of those will will want a dozen upgrades more...
It's times like this I really miss the VMS "stable API with backwards compatibility" mindset.