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451 4.4.0 dns query failed. the error was dns query failed with error retry

    Question

  • Dear All,

    I am facing "451 4.4.0 dns query failed. the error was dns query failed with error retry" error on exchange server 2016. mails stuck in que. please guide.

    Regards

    Sajid

    Monday, March 12, 2018 10:57 AM

All replies

  • Hi Sajidami82,

    Things we want to confirm with you: Could you please help to verify the following information for further troubleshooting?
    1. Do you have any firewall installed? Any firewall settings blocking this if you have installed and configured?
    2. This issue only occur on a specific domain or all domains which you try to send mails to? Does this issue only affect specific domain or all of the domains?
    3. Enable the Protocol logging, can you get a detail error message in it?( Exchange Server\V15\TransportRoles\Logs\Hub\ProtocolLog\SmtpSend)

    We can enable the protocol log, and check if any error messages in the logs.
    Path: 
    C:\Program Files\Microsoft\Exchange Server\V15\TransportRoles\Logs\FrontEnd\ProtocolLog\SmtpSend
    Or
    C:\Program Files\Microsoft\Exchange Server\V15\TransportRoles\Logs\Hub\ProtocolLog\SmtpSend

    You can also have a look whether your domain and server IP of Exchange server in a blacklist via the MXTOOLbox.

    If this issue occur on all domain, make sure your DNS settings are working properly. 

    Regards,

    Kyle Xu


    Please remember to mark the replies as answers if they helped. If you have feedback for TechNet Subscriber Support, contact tnsf@microsoft.com.

    Click here to learn more. Visit the dedicated forum to share, explore and talk to experts about Microsoft Teams.

    Tuesday, March 13, 2018 12:32 PM
    Moderator
  • Hi

    Can you telnet from the server on port 25?

    Are your MX records in place to route mail? Please check MXtoolbox and see if all records are showing and that you not on any blacklists.


    Hope this helps. Please remember to click “Mark as Answer” on the post that helps you, and to click “Unmark as Answer” if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.

    Tuesday, March 13, 2018 7:05 PM
    Moderator
  • Hi Sajidami82,

    Any update now?
    If the above suggestion helps, please be free to mark it as answer.

    Regards,

    Kyle Xu


    Please remember to mark the replies as answers if they helped. If you have feedback for TechNet Subscriber Support, contact tnsf@microsoft.com.

    Click here to learn more. Visit the dedicated forum to share, explore and talk to experts about Microsoft Teams.

    Monday, March 19, 2018 1:56 AM
    Moderator