Manually re-create the folder structure of your sbcglobal.net account underneath the Thunderbird built-in "Local Folders" account. https://kb.mozillazine.org/Local_Folders Then copy over messages from your sbcglobal.net account to the "Local Folders" account on a folder by folder basis. Once everything has been copied over you can delete the sbcglobal.net account. Make sure to create a full backup of your Thunderbird profile prior to start messing with it. https://support.mozilla.org/en-US/kb/profiles-where-thunderbird-stores-user-data#w_backing-up-a-profile Once done, backup your your profile on a regular basis.