Sendmail problem and comcast.net

[Account for Debian group mail <debian@pcez.com>]

Hello


We're having a problem sending mail to comcast.net. The message we are 
getting is:

Aug  7 12:31:18 smtp sm-mta[22694]: m77JV1iC022684: to=<someuser@comcast.net>, delay=00:00:17, xdelay=00:00:01, mailer=esmtp, 
p ri=210588, relay=mx2.comcast.net. [76.96.30.116], dsn=4.0.0, stat=Deferred: 421 IMTA12.emeryville.ca.mail.comcast.net
comcast Reverse DNS failure : Try again later

We are getting this message on different mail servers and comcast.net mail 
is stacking up. I have stopped our DNS server and restarted it in case 
there is a problem there with no difference.

I do a nslookup on mx2.comcast.net and get:

Non-authoritative answer:
Name:   mx2.comcast.net
Address: 76.96.30.116

That checks out... I do a nslookup on 
IMTA12.emeryville.ca.mail.comcast.net
and get:

Non-authoritative answer:
Name:   IMTA12.emeryville.ca.mail.comcast.net
Address: 76.96.30.30

Which is a different IP address. I'm not sure where it gets the 
IMTA12.emeryville.ca.mail.comcast.net address to begin with???

Anyone have any ideas? Does anyone have a phone number to get a hold of 
comcast.net administrators?

Thanks,

Ken