Now, you install a new OS and want to import old mails and settings to the newly installed fresh Thunderbird. How?
- Open thunderbird and close it
- Go to /home_folder/.thunderbird
- Remove already exist *.default profile folder
- Add your back-up *.default profile folder
- Update profile.ini file to show your new profile folder
- Update prefs.js content in your profile folder
- Open Thunderbird again