troubleshooting Question

Mail stuck in Exchange 2010 Queue

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LOGTECHSERV asked on
ExchangeDNS
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We have an Exchange 2010 server running on MS Windows Server 2008 R2. The domain controller (also DNS) is MS Windows Server 2008 R2. Email is getting stuck in the queue for domains like aol.com, yahoo.com, and comcast.com with Error 451 4.4.0
Results from running
nslookup –type=mx aol.com on Exchange server:
DNS request timed out.
    timeout was 2 seconds.
Server:  UnKnown
Address:  207.200.74.38

DNS request timed out.
    timeout was 2 seconds.
DNS request timed out.
    timeout was 2 seconds.
*** Request to UnKnown timed-out

From the DNS server
Server:  localhost
Address:  ::1

DNS request timed out.
    timeout was 2 seconds.
*** Request to localhost timed-out

From the DNS server
nslookup -type=mx google.com

Server:  localhost
Address:  ::1

Non-authoritative answer:
google.com      MX preference = 400, mail exchanger = google.com.s9b2.psmtp.com
google.com      MX preference = 100, mail exchanger = google.com.s9a1.psmtp.com
google.com      MX preference = 200, mail exchanger = google.com.s9a2.psmtp.com
google.com      MX preference = 300, mail exchanger = google.com.s9b1.psmtp.com

google.com.s9b2.psmtp.com       internet address = 74.125.148.14
google.com.s9a1.psmtp.com       internet address = 74.125.148.10
google.com.s9a2.psmtp.com       internet address = 74.125.148.11
google.com.s9b1.psmtp.com       internet address = 74.125.148.13


We can get on the internet. I get ping responses from Yahoo.com and Comcast.com
From the properties tab in DNS on the server, if I go to the Monitoring tab, “a simple query against this DNS server” passes. However, “a recursive query to other DNS servers” fails. I found online that it might be a problem with the root hints. So I copied them from the old DNS server. I have the forwarders in the same order as the old DNS server. The old DNS server passes both tests and gets responses from aol, yahoo, comcast, etc using the nslookup tool.
Can anyone please give me an idea of where else to look for the root of the problem?
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