Mail app keeps canceling shutdown? Help please

[LouisvilleXV]

So I just got my iMac about a month ago, and roughly 50% of the time when I go to shut down, a message pops up stating that the mail app could not be closed and the shut down was cancelled. I then have to manually go and force quit the application before the computer will shutdown. A google search shows a ton of other people complaining about this issue over the years, but I haven't seen a cause/fix. Any help?

 

[benwiggy]

If an app cancels shutdown, it's because it needs user attention in some way.
Force quitting an app is not a thing you should normally have to do, so you need to find out:
what is happening in Mail;
why does it need Force Quitting;
and what can be done to fix it so that it works normally.

Does Mail bring up any dialog message at shutdown?
Are there any relevant messages in the system logs relating to Mail? (You can find these using "Console" app in Utilities folder.

What happens when you try to quit mail using Command Q when you are not shutting down?

Open the Activity window in Mail (Command alt 0), or from the Window menu. Is any network connection hanging?

 

[satcomer]

Make sure you have nothing sitting in your main Inbox. Then (with Mail closed) open /Applications/Utilities/Terminal.app and run the command:

sqlite3 ~/Library/Mail/Envelope Index vacuum;

Let this run until you get another Terminal prompt. Then try running Mail again, Good Luck.