We have 2 external DNS servers that we recently migrated from Windows Server 2003 to Windows Server 2008 R2. We are experiencing an issue sending mail through our Exchange server and I have narrowed it down to an issue with the DNS servers. If I perform a reverse lookup against one of our external DNS servers the IP address resolves and gives me the name. The issue is when I try doing the exact same thing against an external DNS server that is outside our network For Example: 126.96.36.199. When I do this, I receive the following error.
*** b.resolvers.Level3.net can't find <IP ADDRESS>: Server failed
I have looked at the settings and everything looks like it is configured correctly; however, this still isn't working.
This is not affecting Forward lookups as I am able to resolve these from our External servers as well as servers outside our network.