Microsoft KB Archive/295164

= SMTP Clients Receive Relaying Prohibited Error Message When Authenticated Relay Is Enabled =

PSS ID Number: 295164

Article Last Modified on 10/9/2003

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The information in this article applies to:


 * Microsoft Exchange 2000 Server
 * Microsoft Exchange Server 2003 Enterprise Edition
 * Microsoft Exchange Server 2003 Standard Edition
 * Microsoft Windows Small Business Server 2003, Premium Edition
 * Microsoft Windows Small Business Server 2003, Standard Edition

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This article was previously published under Q295164



SYMPTOMS
When you send mail from a Simple Mail Transfer Protocol (SMTP) client (such as Microsoft Outlook Express) to a computer that is running Exchange 2000 or Exchange Server 2003 on which authenticated relay is enabled, you may receive a non-delivery report (NDR) that contains the following error message:

The message could not be sent because one of the recipients was rejected by the server. The rejected e-mail address was ' @ .com'. Subject ' ', Account: '. .com', Server: '. .com', Protocol: SMTP, Server Response: '550 5.7.1 Unable to relay for ' @ .com', Port: 25, Secure(SSL): No, Server Error: 550, Error Number: 0x800CCC79

In addition, if you use Microsoft Outlook Messaging Application Programming Interface (MAPI), you may receive the following error message:

The following recipient(s) could not be reached:

' @ .com' on 4/1/2001 8:19 PM No transport provider was available for delivery to this recipient.

You may receive these error messages even though the client uses proper credentials to authenticate with the server. Also, a Telnet session to the server on port 25 connects and then immediately disconnects after you press a key.



CAUSE
This issue can occur if the Auth and Auth login commands (Extended Simple Mail Transfer Protocol [SMTP] commands) are stripped by a Cisco firewall/router.



RESOLUTION
To resolve this issue, disable SMTP inspection on the firewall/router. If you do not know the command to disable SMTP inspection, contact Cisco.



MORE INFORMATION
ESMTP commands can also be removed by Pix firewall software.

For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

320027 XCON: Cannot Send or Receive E-mail Messages Behind a Cisco PIX Firewall

The third-party products that are discussed in this article are manufactured by companies that are independent of Microsoft. Microsoft makes no warranty, implied or otherwise, regarding the performance or reliability of these products.

Additional query words: XCON

Keywords: kberrmsg kbprb KB295164

Technology: kbExchange2000Search kbExchange2000Serv kbExchange2000ServSearch kbExchangeSearch kbExchangeServ2003Ent kbExchangeServ2003Search kbExchangeServ2003St kbSBServ2003Pre kbSBServ2003Search kbSBServ2003St kbSBServSearch

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