It takes some work. None of this is due to Thunderbird, but due to email accounts. My response will not address everything you want but may be a start: - for Gmail, rightclick on account, an click 'subscribe' and UNsubscribe from Allmail and Important. Doing that will cut your cpu time and reduce disk space noticably, as that was duplicating all your receives and sends for Gmail. Also, after doing that, exit thunderbird, locate the allmail, allmail.msf, important,important.msf files in your profile and delete them - for Gmail, click server settings then the 'advanced' button and enter [Gmail} (including the brackets) in the IMAP server directory field - for the duplicated file names, check to see which one the oniine account prefers (e.g., on the bt.com site, delete a message and see into which folder it went). Then, in thunderbird, set the delete folder to that folder and then delete the other. This may take a bit of practice because thunderbird provides default names and the actual account may prefer a different one. For unwanted folders, if you cannot delete from within thunderbird, try doing it when thunderbird is not running.