Follow these steps: # locate the Local folders location. You can find that by clicking account settings and scrolling down to local folders and note the local directory on bottom line # now, exit thunderbird and COPY that folder to another drive # next, restart thunderbird and, on that Local Folders pane, click the dropdown menu on Local Directory, and point it to the new location. Thunderbird will probably close and restart # now, check that all is working find with new layout # you may now go to that original Local Folders location in the profile and delete the folders there.