We have an issue sending emails to certain domains, namely Time Warner and Cox. Last week, we decommissioned our Exchange 2003 server and now our Exchange 2010 server is doing all of the transport for our domain. We run our own authoritative name servers, so we are in charge of the DNS and have modified our PTR record to reflect the new server. All mailflow is working except for these 2 domains.

When I telnet on port 25 to the mail servers for Cox and Time Warner I am receiving errors. For Cox the error is: 554... rejected - no rDNS

And when I telnet to port 25 to the Time Warner mail server we get this: 554 5.7.1 - Connection refused. IP name lookup failed for x.x.x.x

I have run through the outbound SMTP test on Microsoft Remote Connectivity Analyzer and get 100% completely successful results. MXToolbox comes up with all successful tests on SMTP as well, showing correct reverse banner check, and no blacklisting. DNSQueries.com shows a valid reverse DNS entry as well for us.

Outbound emails to these 2 domains continue to sit in the queue. Any ideas or advice would be greatly appreciated.

Thanks!