Looking for MX clue at cable.comcast.net

When I try to us the automated form to unblock my server's IP I get:

Correction: It's cable.comcast.com (not .net) and it turns out that
that is the domain used by comcast employees not customers. our mail
gets delivered to comcast customers just fine, just not to comcast

I have to say that the tier 1 person I talked to was fairly clueful
regarding possible issues delivering to comcast customers, but she
didn't have any knowledge about the employee domain.

If postmaster@cable.comcast.com sees this, please give me a call:
435.636.0069. I'd like to get this resolved ASAP.