Users continue to submit possible solutions to an on-going issue where Mail.app seemingly suddenly stops filtering junk mail, and subsequently crashes when attempting to flag messages as junk.
The problem appears to manifest when the user attempts to flag a junk message that has a blank subject and there is already mail flagged as junk in the junk mailbox.
Using an alternative spam filter John Eitner suggests using a third-party spam filter in lieu of Mail.app's built-in junk catching mechanism:
"I think that the JunkMatcher freeware app MAY fix this problem. I installed it today and see no-subject no-sender mail moved into Junk and flagged as having been ID's by JM."
Delete corrupt Junk mail folder Hugo Diaz refined a step-wise process for deleting the corrupt junk mail folder, which is causing this crash in most cases:
- Quit Mail.
- Go to "HomeFolder>Library>Mail>" and then open the folder for your account "POP-xyz", for example (NOT the Mailboxes folder). Inside that folder you'll find that your Junk mailbox got somehow corrupted and is now a simple folder without the '.mbox' extension. Take that folder named "Junk" out of there (or trash it). Then launch Mail again.
- Test the fix by flagging something as junk, it should go to the Junk folder as normal.
- If you look in the Finder, you'll see that your "POP-xyz" folder now contains a "Junk.mbox" file.