How to get Apple Mail to send emails

I've read all to post, had multiple 45+ min phone calls with Xfinity and still no solution. I have the third party app check in the web mail security page. Some post say you have to get an app specific password from Xfinity in the security section but there is nowhere to get that. Other post say you have to get it from your Apple ID page. I did that and still doesn't work. I have trouble with the Xfinity reps I talk with on the phone, broken english and bad connections and a general misunderstanding the problem. How do I get a solution? I will not use Yahoo, gmail, hotmail and others like that as they promote spamming and do nothing to stop it so I need my comcast address to work.