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451 4.4.0 SMTPSEND.SuspiciousRemoteServerError; remote server disconnected abruptly RRS feed

  • Question

  • I have 2 exchange servers that for the most part deliver email as expected. However, there are a few emails that are stuck in queue with the error Last Error: 451 4.4.0 SMTPSEND.SuspiciousRemoteServerError; remote server disconnected abruptly; retry will be delayed.

    This only affects email that is sent from one server to the other. Eventually the emails will either be delivered or an ndr will be sent. Sniffing the connection shows port 2525 in use and almost all email is delivered.

    There servers are in 2 different AD sites. O/S is 2012R2 standard and they have ample resources. Ping times are consistently below 100ms and I can telnet using ports 25 and 2525 from each server to the other with no problem. Any help or insight into what might cause this is appreciated.

    Example from the queue viewer:Delivery Type.......SMTP Relay to mailbox delivery group

    Last Error:

    Identity: Dallas\3\7297149436001
    Subject: FW: Riley Industrial Services, Inc. - New Account Setup Request
    Internet Message ID: <8b4e19b8e78b4a3fb977bdb60e2b70d3@ourdomain.com>
    From Address: ljackson@ourdomain.com
    Status: Retry
    Size (KB): 709
    Message Source Name: SMTP:Default DALLAS
    Source IP: 192.168.21.90
    SCL: -1
    Date Received: 8/10/2016 9:50:51 AM
    Expiration Time: 8/12/2016 9:50:51 AM
    Last Error: 451 4.4.0 SMTPSEND.SuspiciousRemoteServerError; remote server disconnected abruptly; retry will be delayed
    Queue ID: Dallas\3
    Recipients:  khickman@ourdomain.com;3;3;[{LRT=};{LED=451 4.4.0 SMTPSEND.SuspiciousRemoteServerError; remote server disconnected abruptly; retry will be delayed};{FQDN=};{IP=}];0;CN=db1,CN=Databases,CN=Exchange Administrative Group (FYDIBOHF23SPDLT),CN=Administrative Groups,CN=ourdomain,CN=Microsoft Exchange,CN=Services,CN=Configuration,DC=ourdomain,DC=com;0

    Wednesday, August 10, 2016 4:09 PM

Answers

  • Hi

    it can be a grey listing issue, can you ask the receiving parting to whitelist your public ip and see if it delivers?

    If you run a blacklist check from MXtoolbox does your domain come back clean?

    Also check your SPF records.


    Edward van Biljon - Exchange MVP


    Wednesday, August 10, 2016 5:21 PM

All replies

  • Hi

    it can be a grey listing issue, can you ask the receiving parting to whitelist your public ip and see if it delivers?

    If you run a blacklist check from MXtoolbox does your domain come back clean?

    Also check your SPF records.


    Edward van Biljon - Exchange MVP


    Wednesday, August 10, 2016 5:21 PM
  • Hi,

    As Edward’s supplement, please also check the configuration of your firewall if you’ve deployment.

    Then please also check if this issue only affect specific domain or several domains;

    Please check if this issue only affect specific senders in your domain.

    Best regards,


    Please remember to mark the replies as answers if they help, and unmark the answers if they provide no help. If you have feedback for TechNet Support, contact tnmff@microsoft.com.

    Jason Chao
    TechNet Community Support

    Thursday, August 11, 2016 2:27 AM
  • Hi,

    I had a similar problem later it was fixed at the remote server, issue was related to anti-virus blocking the connectivity from source even though the telnet was successful. This issue may or may not be related to AV, however please validate that as well.

    Have you tried exporting the emails from queue and try to replay them? If yes all those email going back to same queue and stuck with same error?

    Thursday, August 11, 2016 9:59 AM
  • Hi,

     

    Would you please provide us with an update on the status of your issue? If the solution helped, if so, please help to mark as answer, it'll be helpful and easily to search for others, thanks for your time.

     

    Best regards,


    Please remember to mark the replies as answers if they help, and unmark the answers if they provide no help. If you have feedback for TechNet Support, contact tnmff@microsoft.com.

    Jason Chao
    TechNet Community Support

    Monday, August 15, 2016 3:34 AM