Need to talk to Charter email contact

Good afternoon, I'm looking for some cluefull help from someone at Charter. I've got a static IP customer unable to deliver mail to customers and I can get no help trying to get in through the 'front door' of tech support. I've been forwarded to the residential spanish technicians 3 times so far to get rid of me.
Customer is unable to get any connection to on port 25 thus is unable to use the<> method of clearing this up. The few people I've talked to that understand what I'm talking about say that his connection timing out is 'impossible to be an issue on the Charter side', but there is no block preventing his email on our side (and he can successfully send to aol, bellsouth, hotmail, gmail, yahoo, comcast, etc..)
DNS is configured with mx, forward and reverse records properly setup.

Can contact me off list by phone or email. Thanks in advance.

And a followup I've got someone in their mail group and we're working on clearing up the issue.

Thank you everyone for the replies and help.