SMTPSEND.SuspiciousRemoteServerError RRS feed

  • Question

  • Hi Friends i need your help , i have some troubles with my email .I have a server with so 2003 and exchange 2003 sp2 ,  I can send and receive emails to most domain, but users or companies that use the 365 service office can not send me emails, the server returns them SMTPSEND.SuspiciousRemoteServerError mistake; remote server disconnected abruptly - returned 451 4.4.0  .They're going to say that the 2003 exchange is very old but until now had worked perfectly. 
    Monday, August 31, 2015 4:30 PM

All replies

  • Hi,

    During my research, I find some information for your reference.
    For the NDR “451 4.4.0 SMTPSEND.SuspiciousRemoteServerError; remote server disconnected abruptly; retry will be delayed”. This message may be caused by the firewall SMTP Fixup protocol when using TLS encryption. If this is the case, please try to disable it to see if it helps. Also, please add this problematic email address or domain to white list for testing;

    Meanwhile, please ensure that SPF record for your domain is formal.

    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

    Allen Wang
    TechNet Community Support

    Tuesday, September 1, 2015 3:24 AM
  • My domain is   , I disable all firewall rules but did not work
    Wednesday, September 2, 2015 5:18 PM