Mail box contents disappeared

Question

After a failed Tech Tool treatment I had to erase my hard drive and restore it from a back-up. In the process the contents of my inbox, and one of my mailboxes, disappeared. Can I retrieve them, and if so how?
Any advice would be greatly appreciated

Answer 1

So you have some plug-ins. I wonder whether they could have a bearing on this. If the procedure I’ll suggest below doesn’t work, you should consider (properly) uninstalling them and try again.
Assuming there is nothing wrong with the filesystem (you may want to verify the startup disk with Disk Utility, just in case), try this:
1. Quit Mail if it’s running.
2. In the Finder, go to ~/Library/Mail/. Make a backup copy of this folder, just in case something goes wrong, e.g. by dragging it to the Desktop while holding the Option (Alt) key down. This is where all your mail is locally stored.
3. Locate Envelope Index and move it to the Trash. If you see any other “Envelope Index”-named file there, delete it as well.
4. Move any “IMAP-”, “Mac-”, or “Exchange-” account folders to the Trash. Note that you can do this with IMAP-type accounts because they store mail on the server and Mail can easily re-create them. DON’T trash any “POP-” account folders, as that would cause all the mail stored there to be lost.
5. Open Mail. It will tell you that your mail needs to be “imported”. Click Continue and Mail will proceed to re-create Envelope Index — Mail says it’s “importing”, but it just re-creates the index if the mailboxes are already in Mail 2.x format.
6. As a side effect of having removed the IMAP account folders, those accounts may be in an “offline” state now. Do Mailbox > Go Online to bring them back online.
Note: For those not familiarized with the ~/ notation, it refers to the user’s home folder. That is, ~/Library is the Library folder within the user’s home folder, i.e. /Users/username/Library.