Email Stuck In Local Delivery Queue - 451 4.4.0 DNS query failed

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Email's are stuck in local delivery queue with error 451 4.4.0 DNS query failed

External mail flow incoming & outgoing is working fine, Only internal mail flow is impacted.

  

Application Log an event id 16025

Log Name: Application
Source: MSExchangeTransport
Date: 10/16/2015 12:59:51 PM
Event ID: 16025
Task Category: Configuration
Level: Error
Keywords: Classic
User: N/A
Computer: XXXXX.XXXX.XXXX
Description:
No DNS servers could be retrieved from network adapter 32ddc2da-4531-4553-b3f0-ebd756d504c0. Check if the computer is connected to a network and Get-NetworkConnectionInfo returns any results.

DNS is configured correctly, Name resolution is working as expected & Network Configuration is correct.
Ran command Get-NetworkConnectionInfo however could not find the GUID mention in the application logs.
We could not find the GUID anywhere on the server, even in the registry.

 

So where is the GUID coming from and why Exchange is looking at it ?

We ran below command and found the Network Adapter GUID that was listed in application logs

Get-TransportServer -Identity XXXXX | Fl Name,ExternalDNSAdapterGuid,InternalDNSAdapterGuid

Name : XXXXX
ExternalDNSAdapterGuid : 32ddc2da-4531-4553-b3f0-ebd756d504c0
InternalDNSAdapterGuid : 32ddc2da-4531-4553-b3f0-ebd756d504c0

This means Exchange will only us this network adapter for name resolution internally, as there was no network adapter with this guid on the Exchange server, DNS query failed.

 

How to resolve this ?

We ran below command and restart Microsoft Exchange Transport Services, Mail flow started to work. :D

Set-TransportServer -Identity XXXXX -ExternalDNSAdapterGuid 00000000-0000-0000-0000-000000000000 -InternalDNSAdapterGuid 00000000-0000-0000-0000-000000000000

 

Why this GUID ?

Putting the GUID as 00000000 means Transport will use any network adapter that is available on the server for DNS query and will not be binded to any single network.

 

 

Note : This Resolution May Or May Not Apply Depending On The Error.

You can also look at

https://officeserversandservices.com/2014/09/19/exchange-2013-cu5-edge-issue-with-dns-event-id-2000/