Last Error: dns query failed in queue exchange 2007/2010 Posted on February 16, 2012 by dpejic Firstly, make sure your firewall has an exception for DNS (UDP 53) and SMTP (TCP 25)If you cannot successfully ping the smart host and receive a reponse within a few seconds, I'd suggest clearing the cache of your Internal DNS Server then restarting the DNS Server service on your DC, and restarting Microsoft Exchange Transport Service too. If this not help try this: on hub set in edgesync – default–first–site–name to Internet / network/ check Use the External DNS lookup settings… next use start-edgesynchronization on edge goto properties of edge transport server, external dns lookups and set "use network card dns setting" on y internet-conected card, ok and done 🙂