Yes, I would enjoy a free bottle of George Dickel, but we're a free resource. :).. We do this because we like to assist. What you're experiencing sounds like a technical interruption. When you have multiple sent folders, that is indicative of 'something' preventing Thunderbird from saving files at shutdown. antivirus? firewall? other stuff? I don't know, but something is interfering. If you have a proprietary antivirus, my first suggestion is to see if there is a setting to ignore email. if no such setting exists, I suggest temporarily shutting the antivirus down. check your profile for further issues, such as multiple prefs.js files.

David, Thank you for your reply. The anti-virus software is Windows Defender and it has been set to exclude the directories where mail is stored. I also ensured that there is only one prefs.js for Thunderbird (several prefs.js for Firefox, and I assume those are irrelevant).

What "further issues" should I look for in prefs.js?

Thank you again.

Mark