There is a Help article on this: https://support.mozilla.org/en-US/kb/moving-thunderbird-data-to-a-new-computer I'll also add my method: '''1. '''First make sure you have the same version of Thunderbird installed on both computers. On new computer - install Thunderbird and run - it will ask for Mail accounts - but you want to get all data from old computer so do not bother and exit Thunderbird. I'm assuming you are using a Windows OS and all profile data is in the default location. '''2. '''Exit Thunderbird - it's important that on both computers Thunderbird is not running - so close. '''On Old Computer:''' # In window search type: %Appdata% - see image below as guide # Select the %Appdata% file folder # select 'Roaming' # Copy the 'Thunderbird' folder to an external drive '''On NEW Computer:''' # In window search type: %Appdata% - see image below as guide # Select the %Appdata% file folder # select 'Roaming' # Delete the default 'Thunderbird' folder # Paste the copied 'Thunderbird' folder into the 'Roaming Folder' Start Thunderbird.