I'm running site-wide. All SPAM gets pushed into the user's Junk-Mail folder and also copied to another account that is used ONLY to hold SPAM mail. I review the alleged SPAM in the spam account, then run the bayes classifier on it. I then decided to route all high scoring SPAM straight to /dev/null. I now have most of my SPAM going to /dev/null and fewer SPAMs going to the Junk-Mail folder. Me likes :)
I for one would be interested in the nut and bolts of your setup. I'm really interested in how you push mail tagged as spam around. Are you using ProcMail?
"Conformity is the refuge of the unimaginative."