Mac OS X Lion: Fix corrupt Mail folder

On Mac OS X Lion, it happened to me that the mail settings or messages were missing. Checked ~/Library/Mail folder, the messages are still there but I could not see them in Mac Mail. The solution for this is:

• Quit your Mac Mail
• Backup Mail folder:

  cp -r ~/Library/Mail /tmp/
  

• Remove Envelope Index file:

  rm ~/Library/Mail/Envelope\ Index
  

• Open Mac Mail application, it will import the messages automatically
• Quit Mac Mail after import, then re-launch Mac Mail, you will see all the messages
• Remove the backup if everything is ok:

  rm -fr /tmp/Mail