If there is a problem with the application itself, you may just download it and install it again.

Your mail is stored separately from the application. On a Mac, your Thunderbird data would be stored in ~/Library/Thunderbird/, where the '~' at the beginning represents the user home folder. If you have a backup of your data, you just have to restore that folder to get access to your mail again.

Thank you. I'm preparing for meetings now and I'm having other computer problems to work around. I bought a new copy of Microsoft Office 2024, but can't install it, so i can't copy and paste anything from a doc for this meeting. I'll try this suggestion as soon as i can. I find the way gmail is organized on my computer when i access it directly is much more cumbersome and time consuming than via Thunderbird. I don't know if my emails and other info in Thunderbird is backed up or not. Thank you again.

Also see https://support.mozilla.org/en-US/kb/installing-thunderbird-linux

Thank you Wayne. David GG wrote that "your Thunderbird data would be stored in ~/Library/Thunderbird/", but when i search in my Finder (on my macbook pro) nothing pops up. So i'm a little nervous that it might not be on my computer. Maybe relevant - the memory broke the last week in Dec, so i got a new logic board the first week in January, then the new memory broke so i got another new logic board in Feb. I get popups that "One Drive is Damaged" or Thunderbird is Damaged" - with a suggestion to put it in the trash - although not as often as i did before the most recent new logic board. I opened the link that you, Wayne, provided and it lead to how to install Thunderbird on a Mac. Great. It looks like instructions for installing Thunderbird for the first time. So - if i install it as it, per those instructions, then i should be able to transfer my Thunderbird history there? I've backed up my computer via Time Machine before getting each new logic board, then i did a complete upload (download?) from TM to my new board. So i'd guess that my Thunderbird info should have transferred to my new logic board. Right? But i can't find it. I don't want to do anything that might risk losing all my Thunderbird data - i'm not very intuitive re my computer. Years ago i hired a man to help me (he's not doing computer help anymore) - he's the person who installed Thunderbird, saying, i'd love it. He was right. He also once told me just to do what makes sense - or something like that. I replied that when he encounters a problem at the computer - he sees one path forward. When i'm in that situation - i see multiple paths - many of which could lead me into deep trouble. Thanks again.

I opened the link that you, Wayne, provided and it lead to how to install Thunderbird on a Mac. Great. It looks like instructions for installing Thunderbird for the first time. 1. So - if i install it as it, per those instructions, then i should be able to transfer my Thunderbird history there? 2. I've backed up my computer via Time Machine before getting each new logic board, then i did a complete upload (download?) from TM to my new board. So i'd guess that my Thunderbird info should have transferred to my new logic board. Right? But i can't find it.

Sorry for not replying sooner - this systems notifications have been bad for a while.

2. Yes. In ~/Library/Thunderbird/ you should see a Profiles directory.