Microsoft KB Archive/168781

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XFOR: Sending to SMTP Gets Immediate NDR 550 Error Message

Article ID: 168781

Article Last Modified on 10/27/2006


  • Microsoft Exchange Server 4.0 Standard Edition
  • Microsoft Exchange Server 5.0 Standard Edition

This article was previously published under Q168781


All users are receiving Simple Mail Transfer Protocol (SMTP) mail; however, sending to SMTP addresses results in an immediate non-delivery report (NDR) that includes the following error message:

550 Relaying mail to <recipient address> is not allowed.


To work around this problem, do the following:

  1. Confirm that the information store, the message transfer agent (MTA), and the Internet Mail Service (Internet Mail Connector in version 4.0) services are started, by going to Control Panel and double-clicking Services.
  2. Check the configuration of the Internet Mail Service, especially the address space page, which should be a (*) or (a space).
  3. Set all the categories of the Internet Mail Service diagnostic logging to maximum, and then send a message and check the event viewer for errors related to the Internet Mail Service.
  4. Check the four queues of the Internet Mail Service, and the Exchange Server \ Message Transfer Agent \ Internet Mail Service (Server Name) queue. If there are no messages in any of the queues, then the problem may be with the Internet Service Provider (ISP). Go to step 5.

If there is no MTA object under the sender's server, the Exchange Server computer is a Standard Edition, and you must use the Performance Monitor \ Qlength counter of the MSExchangeIMC Object in order to check the Internet Mail Service queues.

  1. Send a message to the sender's ISP. If the sender does not receive the immediate NDR, then ask the sender to call his or her ISP and ask whether he or she received a message. If the ISP received the message, then the Internet Mail Service is able to send, and most probably the ISP is not routing or resolving names.
  1. Run the NSLookup utility to confirm the domain name, MX records, and the A-Records of the sender's ISP.
  2. Run the Telnet command to port 25 of the ISP according the Knowledge Base article: 153119, "XFOR: Telnet to Port 25 of IMC to Test IMC Communication."
  3. If the sender is using DNS, modify the Internet Mail Service to forward all messages to the host. If this works, then the Domain Name resolution is the cause of the problem.
  4. If all the above fails, then delete and recreate the Internet Mail Service.

NOTE: After every step, stop and restart the Internet Mail Service and see whether all messages are being delivered.

Keywords: kbprb kbusage KB168781