"Cannot Get Mail"

"The mail server "imap.comcast.net" is not responding.  Verify that you have entered the correct account info in mail settings.  Server code "AUTHENTICATIONFAILED", server message"

When I travel out of the US my xfinity email stops sending/receiving and I need to access it through the xfinity website.  When I get back to the US I delete the app and then reinstall it.  This time I get this error message when trying to reinstall the email address on my mail app on an iphone.

Any advice?