cannot access my Xfinity (Comcast.com) email

I can no longer access my Xfinity (Comcast.com) email from my Windows computer or from any of my other devices, using either Outlook or Thunderbird email apps. Both mail apps have been working with my Comcast email just fine for years, but all of them quit working early this week. The error message I get is: "Can't find IMAP server"