Tabs settings are saved only on shutdown. It is conceivable that the update failed for some reason to save the tabs. But once they are missing there is no retrieving a previous set of tabs.

This was important to know. Thank you.

I do wonder that they do not warn you before you trust an "update".

The thing is, it was not just the tabs that disappeared, but those emails themselves.

They were important to keep. I never had that issue before with an update.

If you are able to ask them to put in a warning when they offer the update, I would appreciate it. I will take precautions before running an update from now on.

Thanks for the input.

Reload those important messages from your backup that you surely created.

Airmail said

Reload those important messages from your backup that you surely created.

I know nothing about a back-up. No, I did not create that. Wish I had known when I first started.

I have had Thunderbird for years, and never had this issue before.

I will try to look up how you back it up.

Thanks.

This tells you how to backup your profile.

https://support.mozilla.org/en-US/kb/profiles-tb

This tells you how to backup your profile.

https://support.mozilla.org/en-US/kb/profiles-tb

Airmail said

This tells you how to backup your profile. https://support.mozilla.org/en-US/kb/profiles-tb

Thank you so much!  :)