TB should open received messages or new ones in a window that has the same size and position as the last window of that type that was opened, even between TB restarts. So, if you set the size and position, it will be remembered. If it isn't, try this: Help/Troubleshooting, click Show in Finder, close TB, rename xulstore.json, restart TB. Note that this the same as 'Reset toolbars and controls' from the safe mode prompt, and will reset any toolbar customizations (xulstore is the modern version of localstore.rdf).

Thanks,

I had to do the safe mode prompt checkbox as the json file was MIA. Yes, I did search for it before closing Thunderbird. I suspect it is in a hidden folder.

Messages now display in the correct position. Thunderbird still opens wider that it should.

Robert

To fix the main TB window not remembering its size and position, you may have to also delete session.json from the profile folder, while TB is closed.

So it worked once or twice but then the mail windows went back to opening across most of the screen.

Will try the Safe Mode checkbox again and the session.json.

This is most annoying.

macos 10.13.6, Thunderbird 68.5.0 64bit.

Thanks, Robert