You can download any past version of Thunderbird from here:

https://ftp.mozilla.org/pub/mozilla.org/thunderbird/releases/

Zenos said

You can download any past version of Thunderbird from here: https://ftp.mozilla.org/pub/mozilla.org/thunderbird/releases/

Thanks but unless I KNOW that I will be able to retain all my existing emails, I am not certain I would want to "reload" from scratch. Do you now (for a fact) that simply re-loading an older version would retain my existing emails?

Thunderbird is designed, as are many programs, to separate the data from the program. If you uninstalled Word, you wouldn't expect all your .docx and .doc files to go too, would you?

You can uninstall and reinstall the Thunderbird program, and the data files (in your so-called profile), remain untouched.

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

However, you can and should make a backup copy of your profile so you can get back to where you are now if anything behaves unexpectedly.

Thanks. I was able to verify that the trash folder was corrupted. Simply removing the trash & trash.msf hasn't worked but I do have a second trash file in th elocal folders so I am working temporarily using that for now. I will delete the existing TB program and then re-install over the weekend backing up data in advance.