If you are a user of Mozilla Thunderbird and ever find that your Inbox is completely blank one day then try the following method to restore it:

  1. Tools > Account Settings..., select the offending account
  2. Choose Server Settings, then navigate in Window Explorer to the listed path under 'Local Directory'
  3. Close Thunderbird
  4. Delete the Inbox.msf in the directory that was listed under 'Local Directory'
  5. Restart Thunderbird

This should then rebuild your Inbox folder and bring back all your missing mails.