A friend has been having problems with Mail. Notably, Time Machine is no longer working within Mail, and Mail says it has huge and seemingly arbitrary numbers of messages in the title bar.
For example, while looking at a folder that clearly has just a couple dozen messages, the title bar says something like: "Inbox (6487431079 messages, 524981056 unread)". This is similar, with different numbers, for every mailbox. We ran out of time and I did not try it on a brand new mailbox.
This happened after my friend switched Internet providers, and all his old email disappeared. I tried "Mailbox --> Rebuild" to no avail. While in Mail, Time Machine showed no messages backed up since the switch, and no messages at all prior to the switch. He was using POP for both providers.
Using Finder, I looked through his backup disk, and found the old email and restored it manually, but it still has those strange numbers, and Time Machine does not work within Mail, although it still seems to be backing up his ~/Library/Mail folder.
I tried quitting Mail, deleting his ~/Library/Preferences/com.apple.mail.* files, and re-starting, but no change in the weird numbers.
He was quite behind in updates, and I cycled through Software Update until nothing else installed -- still weird numbers. (This is Snow Leopard.)
Is there some other preferency file I should be deleting to fix this? Any other ideas?