The weirdest thing happened when I compacted my Mozilla mail mailboxes: every single mail now appears twice in the folder listing, but one of each of the duplicates does not contain the email and cannot be deleted. It's just a void entry.
Anyone know how all that is indexed and if it is safe to kill the index file (if any)?
Update: there are some .msf files in the mail folder that appear to be indices. Deleting them and restarting mozmail fixed the problem, so you know what to do if you hit the same bug.