There are two ways. 1) If your account is IMAP, create the account in your new installation and it will get all the saved and sent emails that are on the server. The server acts like a backup for any folders you created and synchronised with it. 2) If you can access the files on your old hard drive you can copy from it your former Thunderbird profile. This is a folder that contains everything -- account settings, contacts, filters etc. The details are here: https://support.mozilla.org/en-US/kb/profiles-tb I suggest you read the whole thing, though 'restoring to a different location' is the most relevant bit for you. For the future, if you make regular backups of your Thunderbird profile you won't find yourself in this predicament again. I make a safe copy of mine every week, some people with lots of traffic do it daily.