Recently, while working on an issue with Email Delivery on Microsoft Exchange 2007 Service Pack 3 Servers.

Environment: Exchange 2007 Hub & Exchange 2007 Edge Servers separately configured.

Analysis: Further checking on the issue found the following error message on the Exchange Server Messaging Queue:

HOSTS file not used 451 4.4.0 DNS query failed

After a lot of research and wasted hours, I was able to figure out the solution which worked for me. Hoping that this shall also help you.

Solution: Under the Network Binding order, “Network Connections – Advanced – Advanced Settings”, ensure that you have the proper Network Adaptor on the top of the list. You can also consider to disable any unused Network Adaptors on the Servers. This shall be a very good practice.

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Passionate for Latest Gadgets, a Computer geek by Hobby, and luckily Profession too. Started my career in 2005 with IBM, worked with Microsoft later. Back in 2009, started Pledge Technologies ( (parent company to Grishbi). We, at Pledge Technologies, provide IT Consulting to SMBs across US & UK. Specialized in Microsoft Technologies like AD, Exchange, etc., and lot of experience of Office 365 Migration for various clients. Grishbi is a platform where we express what we learned today, and share it with world.