Still cannot send mail via apple mail

Yes, just sending emails.  Set to imap.  With Comcast’s email and password.  Box is checked in security on my email accounts allowing third party access.  Used all the port numbers suggested.  Restarted my modem.  Removed an account and added ir back again still no change.

Thank you so much for sharing those details with us, @user_f0bxt3! Can you attempt the steps below and see if that helps?

Consider an App-Specific Password (Less Common for Comcast)
While primarily a Google/Apple/Yahoo feature, some older security changes at Xfinity may cause the mail client to reject your main password for security reasons. Although you mentioned changing the password, this step is worth verifying as a secondary layer of security:

- Check your Xfinity Account Security: Log into your Xfinity account on the web. Look for settings related to "App Passwords" or "Third-Party App Access Security."

- Action: If there is an option to generate an "App-Specific Password" or similar, generate one and use that password instead of your main Xfinity password when setting up the account on your Apple Mail clients.

I don’t have an app-specific password option under the security tab.  The box for 3rd party access is checked.

Thank you so much for checking the additional password and ensuring it wasn't a concern @user_f0bxt3! Are you able to log in here and send an email from the Comcast connect page? 

Yes, I can send email from all my accounts via Comcast login to my account and going to my email. I just sent an email from one of my accounts to the other Comcast’s email account works fine.