This happened to me once before and the Apple help line's solution was an incredible pain. Hoping someone here can provide a better solution.

Mail worked just fine for a long time with the junk filter. Suddenly, today, the junk filter no longer sends junk-mail to the junk folder. When I try to mark junk mail as junk, Mail crashes and quits.

When this happened before, the Apple help guy told me I had to create a whole damn new system account and move everything to there. You can imagine how fun that was. I'm still running into permission issues with folders from that move.

It strikes me that there must be corruption in some file associated with the junk filter - I just don't know which file it is or where it's hidden.

If anyone has any thoughts that might help with this, I'd be extremely grateful.

Thanks in advance!
-Ravi

That'll teach me to post before searching. Old posts indicate that resetting the junk mail filters in prefs clears the problem up. Tried it and it works.

Amazing (and annoying) that Apple Support didn't come up with that.

Deleting the following file will reset mail Junk, though you'll have to "retrain" it.
First, quit Mail, then navigate to the file.

In your home folder the path is:

Library/Mail

In the Mail folder you will see a file called LSMMap2. Just drag it to the trash, while Mail.app is closed, and then empty the trash.

Note you will have to retrain the spam detection system after deleting the file.