If you use Windows, there is no need to back up the Local folder. And the backup of roaming folder can be reliable done with these steps: I include both the backup and the restore: '''BACKUP''' # ensure thunderbird is not running # enter %appdata% in search window on task bar and press Enter key # this should open windows file explorer in Appdata\roaming folder # highlight the Thunderbird folder and copy to external media '''RESTORE''' # ensure thunderbird is installed, has run at least once, and NOT running now # enter %appdata% in search window on task bar and press Enter key # you should be in Appdata\roaming folder , copy&paste the exported Thunderbird folder there. This may prompt to overwrite an existing folder of same name. allow it # start thunderbird and all should be there