Can you clarify a point? Do you mean A) the emails that were opened in a tab were deleted, so no tab open and no email OR B) the emails are ok, but the tabs were closed, so you had to reopen them. You expected the tabs to reopen as per last session?

Whilst a selected email was open in a tab, did you move that email from one folder to another ?

Do you use a product like CCleaner or similar which cleans up temp files ?

It is known that such products can delete important files such as session or password files. It is advised that you do not allow any type of product that cleans up files any access to any thunderbird file or folder.

Help/Troubleshooting, click Open Folder, close TB, delete or rename session.json. Open and close TB a few times and see if it opens in the same state as when it was last closed.

Toad-Hall B the email tabs I had opened were closed so I had to re-open them. I didn't move any files. The only thing I use to remove temp files are Microsoft Windows 10. Thanks for your help. Jackmo

sfhowes, I did as you said & it still closes all open tabs. Thanks, Jackmo

sfhowes success!! I tried what you suggested again & this time it worked. I opened & closed a few times & it came up as it was before. Can you explain how/why this works?

Thanks again for all the help...this site is great!!!! Jackmo

The session.json file stores the list of tabs that were open at last closing, the folder that was open, and other things. It can be viewed in a text editor.

Thanks for the explanation. Jackmo