I just setup an Edge server, together with 2 Ex2013 servers with DAG. Sync works fine, however incoming mails are stuck at the edge server. The queue looks like this:
451 4.4.0 DNS query failed. The error was: DNS query failed with error ErrorRetry
Checking the logs, it also shows errors like this:
2014-07-12T16:32:06.599Z,08D16C05D02E2774,SMTP,"ex2.internal.contoso.com,ex3.internal.contoso.com,ex4.internal.contoso.com",>,DNS server returned ErrorRetry reported by 0.0.0.0. [Domain:Result] = EX2.internal.contoso.com:ErrorRetry; EX3.internal.contoso.com:ErrorRetry; EX4.internal.contoso.com:ErrorRetry; 2014-07-12T16:32:06.599Z,08D16C05D02E2774,SMTP,"ex2.internal.contoso.com,ex3.internal.contoso.com,ex4.internal.contoso.com",-,"Messages: 0 Bytes: 0 (The DNS query for 'SmartHostConnectorDelivery':'ex2.internal.contoso.com,ex3.internal.contoso.com,ex4.internal.contoso.com':'e01d6f93-e25b-4e36-9f2f-c1c7c73889ae' failed with error : ErrorRetry)"
Now the network is a little special, as the edge server is not in DMZ, but simply in a workgroup in the same LAN as the other Exchange servers. The edge server NIC's are configured to use the internal AD DNS servers, and the edge server is able to lookup all the other exchange servers (ie. ex2.internal.contoso.com).
So I wonder why the edge servers logs DNS lookup errors as long as the server it self can lookup the internal hostnames for Exchange.
Any help would be great, as all incoming mail is now stuck at the edge server.