I run an email server for my business. I have been receiving reports from others that emails were bouncing back, so I tested on my own personal comcast email address. Sure enough, I get no delivery, and then the temporary failures start rolling in later. I eventually get a permanent failure message. Checking my logs, comcast's mail servers are not even attempting to connect. I have no delivery problems for any other email services.
I'm hoping @ComcastCSAEmail can shed some light on what's going on or point me to someone who can see why this is getting blocked.
Bump - I've called worked with comcast phone support twice and been escalated to "advanced level support." Twice I was supposed to get a call back on this issue one time I did receive a call back, but the agent said that the ticket was already escalated above his department, and I would receive another call back. The second time I worked through the first two levels of support, I was supposed to receive a call back the next day. I still have not received a call from "advanced level support."