Exchange 2016 unable to send emails with Exchange 2010 as Hub Transport

Quentin Roberts 106 Reputation points

In the process of migrating from Exchange 2010 to Exchange 2016.

Currently Exchange 2010 is the Mailbox, Hub Transport, and Client Access server. Exchange 2016 is only a Mailbox server.

I want to verify mailflow between the 2 Exchange servers and currently it isn't working.

Current environment is like this:

Internet --> Sonicwall Email Security Virtual Appliance (spam smarthost) --> Exchange 2010

Exchange 2010 is working fine to send and receive emails that are external or mailboxes stored on its database.

However I cannot get Exchange 2016 to send emails externally (outside of the domain) or send emails internally (to mailboxes either on Exchange 2010 or Exchange 2016).

I checked the Message Tracking logs on Exchange 2016 and I see this error:

S:ItemEntryId=00-00-00-00-4F-AE-F9-BB-EF-20-ED-4B-B0-C6-7C-88-01-33-D1-DB-07-00-EE-FA-5A-AE-64-B2-A9-47-93-F1-13-72-CF-E6-C7-EF-00-00-00-00-01-0F-00-00-EE-FA-5A-AE-64-B2-A9-47-93-F1-13-72-CF-E6-C7-EF-00-00-00-00-19-F0-00-00;'S:DiagnosticInfo=Error: RetrySmtp, Diagnostic Information: Stage:UpdateMsgIdToPoisonContextMapping, SmtpResponse:451 4.4.0 DNS query failed. The error was: SMTPSEND.DNS.NonExistentDomain; nonexistent domain mailboxtransportsubmissioninternalproxy -> DnsDomainDoesNotExist: InfoDomainNonexistent, details:FailedRecipientCount:0; RetryRecipientCount:0';S:DeliveryPriority=Normal

I am not sure why Exchange 2016 cannot resolve the internal domain or external domains. In the IPv4 settings in the network adaptor the DNS settings are set to our domain controller and I am able to resolve and ping each Exchange server to/from each other so they are able to resolve and see each other on the network.

What other things should I be looking at to find out what's going on with the mailflow?

Exchange Server Management
Exchange Server Management
Exchange Server: A family of Microsoft client/server messaging and collaboration software.Management: The act or process of organizing, handling, directing or controlling something.
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Accepted answer
  1. Quentin Roberts 106 Reputation points

    Okay I have resolved the issue.

    1) Had to update the DNS settings in the NIC on Exchange 2016 to reflect the same settings on Exchange 2010. This resolved the incoming email issue.

    2) On our email spam appliance (Sonicwall Email Security Virtual Appliance) I needed to add the new Exchange 2016 FQDN to the source IP for the outbound MTA so mail flow would be allowed on that MTA for outgoing email.

    Right now email is flowing to/from the Exchange 2010 to Exchange 2016 and email is also flowing to/from Exchange 2016 to the internet/domains outside of our network.

    1 person found this answer helpful.

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  1. Xzsssss 8,861 Reputation points Microsoft Vendor

    Hi @Quentin Roberts ,

    Please check this doc: 451 4.4.0 DNS query failed Exchange Server error in message queue

    If you have an external/alternate DNS server for your Exchange servers' NIC, you could remove it and then restart Microsoft Exchange Transport Service to see if it works.


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    1 person found this answer helpful.