If you’re having trouble sending and receiving emails using the Mac Mail app, but you’re sure the settings are right and you’re able to send and receive via the web or an iPhone or iPad, maybe you’re looking for an answer in the wrong place. That’s what I was doing a few weeks ago.
The settings were definitely right. The account worked fine on the iPhone. But nothing could be sent, and nothing could be received, in the Mail app on the Mac.
The answer was “run Malwarebytes and clean up the hard drive.” (You can get Malwarebytes for free and you can read all about it in my Malwarebytes article.) After scanning with Malwarebytes, and then deleting the items that Malwarebytes found, Mail worked perfectly right away.
Maybe this will help you out some day.