For the past week or two MAIL, although seemingly working fine otherwise, does not quit when I choose quit. I also recently noticed popups about messages appearing on the right side of the screen. These never came up before either. I found a way to turn them off in SpamSieve, but MAIL continues to not quit properly. I “suspect”, but haven’t verified that SpamSieve is preventing MAIL from quitting.
The ONLY WAY OUT is to FORCE QUIT MAIL. Not a good plan.