It probably WAS them. Xfinity/Comcast's email system has been sick since yesterday. I think it may be finally working OK for me now (but that could change.) How about you?

Starting yesterday not receiving email from xfinity, xfinity claims it is not them, on my end thunderbird says connection refused.

Sounds like your mail server settings might’ve changed. Double-check the incoming/outgoing server names, ports, and SSL in Thunderbird. Sometimes Xfinity updates those and you need to re-enter them.