I'm having the same problem, google sent me to you. So… what does give?
- underwhelm (guest) 11-20-2003 2:56 pm

I set it back to training mode (in the 'When junk mail arrives' preference setting,) and then when I went back to mail it told me that I had been in training mode for a while and did I wish to move to automatic. I said yes and it started working again.

Good luck.
- jim 11-20-2003 4:49 pm

this didn't seem to work for me for some reason, I found the following on macnn forums which did the job however:
"This is a bug in Panther Mail. It only happens if you have no rules defined at all. A workaround is to create a rule that has no real purpose. The one I used is something like "If From: Contains asdfasdfasdfasdf then set background color to red". Junk foldering works again after that."
cheers
- jon (guest) 11-26-2003 1:38 pm

Just for the sake of completeness, jon is correct. Here's the macosxhints.com entry:

Recently I cleaned up some of my mail prefs and auto-junk filtering stopped working. If I manually marked a message as Junk, it would go to the Junk box, but messages marked as Junk when downloaded would stay in my Inbox.

Deleting prefs and resetting Junk didn't help. What I finally discovered is that if you have no rules at all in your rules list (or one that says "Stop Evaluating Rules"), the Junk rule won't be auto-run either. It now runs after the other rules (whereas it used to run before), and if there are no other rules, then there is no "after" either.

When I created a dummy rule (I even unchecked the "Active" box), Junk automagically started working again.