David Gerard wrote:
How's the antivirus filtering on mail.wikimedia.org? The less obviously dispensible crap in the mailing list queue, the closer it will be to humanly manageable ...
I strongly recommend taking a look at greylisting:
http://projects.puremagic.com/greylisting/
I've run it on two high-volume production mail servers for a few months now without a single legitimate message getting hard-bounced, and the spam volume has dropped tremendously. Adding one or two good, trusted RBLs (say, SBL-XBL) might also be worth considering. Greylisting is trivial to set up with Postfix, by the way.
-IK