Microsoft KB Archive/253703

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SMTP Mail Sent But Not Received When Sent to Certain ISP Domains

Article ID: 253703

Article Last Modified on 2/23/2007


  • Microsoft Exchange 2000 Server Standard Edition
  • Microsoft Exchange Server 5.0 Standard Edition
  • Microsoft Exchange Server 5.5 Standard Edition

This article was previously published under Q253703


Some Internet service providers (ISPs) are currently terminating inbound Simple Mail Transport Protocol (SMTP) mail coming from mail servers on which the IP address has been dynamically assigned. Because many companies use dynamically assigned IP addresses, as provided by their ISPs, this can be an issue. In addition, some ISPs are blocking IP ranges from accepting mail.

When either of these conditions occur, senders do not receive a non-delivery report or any form of notification of the terminated mail from the ISP. The only symptom is that the e-mail message does not arrive. The mail is being terminated after it arrives at the ISP. No error messages are reflected in the SMTP log files on the sender's mail server.


The workaround for this behavior is to relay any mail destined for those specific domain names off an SMTP mail server that allows mail relay and uses a static IP address.


This issue will occur more often as the number of dedicated IP addresses that are available decreases.

Additional query words: dynamic

Keywords: kb3rdparty kbenv kbprb KB253703