... So, while I can't offer a solution, I did want to advise I'm not having a problem with Comcast's web mail. This doesn't mean to say Comcast isn't somehow causing issues for you, but seems to me if the issue was solely on Comcast's end, I would also have a problem, which I'm not.
I can only advise to keep digging into your settings, as there's something contributing to your issue.
Even though you two guys live within spitting distance from one another, totally separate ComCast servers could explain the difference, if in fact the problem is on their end.
