Apple mail is recurrently refusing to send mail on my Mac book pro.

AppleDrivingMeBananas wrote:

I am absolutely fed up with apple's mail programme. It inexplicably recurrently refuses to send mail despite incoming mail working and no issues with my mail on my iPhone. I've had this with my previous MacBook Pro, my iMac and now my new MacBook Pro is doing this. The connection Doctor says that both servers are working. Usually out of frustration, I've just left it and the last few times it did send the mail around 2 hrs after I tried to do it. Surely a mail system should be simple and robust - there must be a major issue with this that Apple cannot fix. Any ideas?

The go to way in dealing with a problematic email account—

delete the account and add it back in

Add or remove email accounts in Mail on Mac - Apple Support