I thought maybe the spammers were getting smarter (but really, who could believe that?). The weird thing was, it was happening on both of my Macs. After perhaps a week or so of this behavior, one machine wouldn't even allow me to drag junk mail over to the junk mail folder by hand. The Mail app would just crash!
I first tried repairing permissions. That didn't help. So I went to the ~/Library/Mail folder and saw this file called LSMMap2, which I knew had something to do with junk mail. I tried to open it up using SubEthaEdit. What do you know. It crashed as well! Something was obviously not right with this file.
Here's what worked for me:
- Make sure Mail is not running.
- Rename LSMMap2 to LSMMap2.old.
- Restart Mail and it will create a new copy of LSMMap2. In my case, it was was quite a bit larger than the old one. I'm not sure why.
- Once you're satisfied that all is well, go ahead and erase the LSMMap2.old file created in step two.

