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Outbound mail stuck in queue

    Question

  • Some but not all emails are stuck in the queue. Error message on Exchange 2010 (SP3) is 451 4.4.0 - connection dropped due to socket error.

    Internal mail is fine, some external mail is fine.  I have recreated the send connector. but it doesn't work, please give me some tips to troubleshoot the issue.

    Tuesday, August 22, 2017 1:13 PM

Answers

    • Look at the queue viewer to see what error is being generated.
    • Enable SMTP protocol logging on the relevant send connectors and see what the connections look like.
    • Use Telnet to port 25 to see if you can connect to the next hop.


    Ed Crowley MVP "There are seldom good technological solutions to behavioral problems."
    Celebrating 20 years of providing Exchange peer support!


    Tuesday, August 22, 2017 5:15 PM
    Moderator
  • Hi,

    Thanks for contacting our forum. It seems a network related issue from the error message.

    Please run the command check the last error in queue: get-queue | fl name, *last*

    It’s also recommended to check if the queued message to the specific domain or random.

    We can also check the protocol of the SMTP send as steps below:

    1) Run following command to enable protocol log:

      Get-sendconnector | Set-sendconnector -protocollogginglevel verbose    

    2) Do some tests to send to/receive from those domains.

    3) Collect the latest SMTP logs from following location on your hub server:               

     C:\Program Files\Microsoft\Exchange Server\V14\TransportRoles\Logs\ProtocolLog\SmtpSend

    Please post out the detailed error message.

    If it’s random, please it’s recommended to update your NIC drivers to the latest version if they’re not and then monitor it.

    By the way, check the event log any errors related transport service and make sure this service is running correctly.

    Hope it helps.


    Regards,

    Jason Chao


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

    Wednesday, August 23, 2017 2:21 AM
    Moderator

All replies

  • What type of Send Connector are you using? Smart host or DNS name resolution?

    Tuesday, August 22, 2017 1:22 PM
    • Look at the queue viewer to see what error is being generated.
    • Enable SMTP protocol logging on the relevant send connectors and see what the connections look like.
    • Use Telnet to port 25 to see if you can connect to the next hop.


    Ed Crowley MVP "There are seldom good technological solutions to behavioral problems."
    Celebrating 20 years of providing Exchange peer support!


    Tuesday, August 22, 2017 5:15 PM
    Moderator
  • What do the outbound messages have in common? Perhaps going to the same domain? The Queue Viewer should show you the last error as well.
    Tuesday, August 22, 2017 6:18 PM
  • Hi,

    Thanks for contacting our forum. It seems a network related issue from the error message.

    Please run the command check the last error in queue: get-queue | fl name, *last*

    It’s also recommended to check if the queued message to the specific domain or random.

    We can also check the protocol of the SMTP send as steps below:

    1) Run following command to enable protocol log:

      Get-sendconnector | Set-sendconnector -protocollogginglevel verbose    

    2) Do some tests to send to/receive from those domains.

    3) Collect the latest SMTP logs from following location on your hub server:               

     C:\Program Files\Microsoft\Exchange Server\V14\TransportRoles\Logs\ProtocolLog\SmtpSend

    Please post out the detailed error message.

    If it’s random, please it’s recommended to update your NIC drivers to the latest version if they’re not and then monitor it.

    By the way, check the event log any errors related transport service and make sure this service is running correctly.

    Hope it helps.


    Regards,

    Jason Chao


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

    Wednesday, August 23, 2017 2:21 AM
    Moderator