I had a client that recently wiped his OS X mail server while attempting to upgrade to Mavericks. I Was able to get the email accounts setup (none of the previous emails were backed up). Authenticating all the Windows machines worked perfectly; however, once I re-authenticated the mac mail accounts all the users old email disappeared. I navigated to ~/Library/Mail/V2 and there was only one inbox file and it was only about 25MB so I have no idea where the email went if it just disappeared. Is there any way for me to get the mail back? I am running out of ideas.