This indicates that the prefs.js file in the profile is not being allowed to be updated when closing thunderbird. it could be an antivirus, or vpn most likely. Or it could possibly be that the prefs.js file is read-only. That is, it's not the IMAP account, it's that anything you do isn't being saved at shutdown. If not sure how to access profile, do these steps: - click help>troubleshootinginformation - scroll down to 'profile folder' and click 'open profile' - you are now in profile and can view the prefs.js file to see when last updated. If you see multiple prefs files, such as prefs-1.js, that is a further indication of the situation.

David, many thanks. The prefs file was read only. Matt.

You are very welcome. :)