Thunderbird & Gmail: Missing Folders

• In Thunderbird, go to Tools – > Account Settings
• Click on Server Settings and scroll to the bottom of the page
• Under “Local Directory:”, click Browse
• Find any missing folder on your hard drive with an *.sbd extension and click “Open”
• Click OK
• Thunderbird will need to restart (“Server Settings: Thunderbird needs to restart now to apply the change to the Local directory settings”).  Once it restarts, Thunderbird should add in your Lionmail folder