[dnanian]

If your emails are cached on your drive, we do back them up. The challenge here is to ensure you don't accidentally "sync" to a server if you've accidentally deleted email (and also emptied your trash), assuming you have an Exchange, Gmail or IMAP account.

So, first make sure any network is NOT available. You don't want to accidentally connect to it.

Then, start up from the backup. Start Mail. You won't be online at this point, so your mail should be whatever was there when you backed up.

Find the email you want, and use Mail's export command to export it somewhere convenient - like on the original drive, in Users/your-user/Desktop (so it's on your desktop) for example.

Then, start back up from your original drive. Import that mail, and there you go.