If you do a repair for that folder do you still have issues with that "missing message"? It's possible to downgrade, but not recommended... You can download the right version for your computer/operating system from here https://archive.mozilla.org/pub/thunderbird/releases/68.9.0/ On the last step of the installation do NOT select to start TB. If you miss this step then on the error that appears ref profile click Exit! *After installed start Thunderbird with this command: --allow-downgrade After that go to Option - Update - change update to manually and disable update service. You might search for updates manually (should suggest 68.12 - this one you are looking for and you can update). Please note that you will need to search on add-ons page the versions which are working with 68.* - those with 78* will might not work. Also you will will probably need to change back the address book by removing .bak to the .mab files (those .bak are a back-up generated by TB when upgrading to v78) *If you don't know how to do that command line check this link with mac instructions: https://developer.mozilla.org/en-US/docs/Mozilla/Command_Line_Options