Here are my suggestions: # install the addon, importexporttools NG, if not already done # click file>offlne/download to ensure that all content is downloaded # highlight inbox folder, rightclick, select importexport option to export mbox to local Windows folder # repeat for each folder to be saved # next, highlight Local Folders, rightclick, select importexport option to import mbox and then select one of the downloaded files # repeat for each folder # now, check the resultant folders to feel confident that you have all the messages # you can now close the IMAP accounts, as you have the content in local folders # finally, I encourage doing a backup as the only copies are now on your PC The safest way (in my opinion) is to back up the entire profile with these steps: '''BACKUP''' # ensure thunderbird is not running # enter %appdata% in search window on task bar and press Enter key # this should open windows file explorer in Appdata\roaming folder # highlight the Thunderbird folder and copy to external media