AOL users with roots in the UK might have noticed that their AOL email no longer works with .com and has been switched to .co.up.
It took me some time to figure out but to the aol.com email to work again in the apple Mail.app you need to generate an 3rd party app specific password with AOL to get it back to work again.
https://help.aol.com/articles/Create-and-manage-app-password