Can't send email using third party app

I have two comcast emails.  One is associated with an existing comcast account and the other one is associated with an old comcast account that was disconnected last month.  Today I can't send emails from the second comcast email associated with the disconnected Xfinity account from my iphone 14 nor from Outlook using laptop.  I can still receive emails but cannot send emails.  I have no issue sending the emails by accessing email from browser.  I also have no issue sending emails from the other email associated with an existing Xfinity account.  So the port/server doesn't seem to be an issue on iphone or Outlook in the computer.  Does anyone know how to fix this?