Archive for May, 2013

451 4.4.0 DNS Query Failed

Posted May 19, 2013 By Jerrid Williams

I recently was helping a customer migrate from Microsoft Exchange 2007 to Exchange 2013 in the same organization and after getting Exchange 2013 installed, we started testing mail routing between 2007 and 2013.  We found that the Exchange 2013 server could route to the Exchange 2007 server, but Exchange 2007 could not route to Exchange 2013.  When looking in the Queue Viewer, we saw that all messages destined for our test mailboxes on Exchange 2013 were stuck in the Exchange 2007 Transport queue with the following status “451 4.4.0 DNS Query Failed”.  It took me a bit to find the culprit and my buddies, Google and Bing did not help too much, so I thought I’d write this up in case someone else ran across the same issue.

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