DOCUMENT:Q260247 06-AUG-2002 [exchange] TITLE :XFOR: Message Looping with Exchange Server on a Windows 2000 DC PRODUCT :Microsoft Exchange PROD/VER:winnt:5.5 OPER/SYS: KEYWORDS:kberrmsg kbnetwork exc55 ====================================================================== ------------------------------------------------------------------------------- The information in this article applies to: - Microsoft Exchange Server, version 5.5 ------------------------------------------------------------------------------- SYMPTOMS ======== If Exchange Server 5.5 is installed on a Microsoft Windows 2000 domain controller, some Internet e-mail messages may loop if the following conditions are met: - The Windows 2000 domain is .com. - The Exchange Server Simple Mail Transfer Protocol (SMTP) site address is .com. - The domain .com does not have an MX record configured in DNS. - Exchange Server is configured to reroute all e-mail messages except e-mail messages to .com (set to deliver inbound). - A message is sent to .com. The following events may be logged in the application event log: - Event ID: 4115 Event Type: Error Event Source: MSExchangeIMC Event Category: Internal Processing Description: The message from the spool file seems to be looping through the routing extension for the Internet Mail Service. Please check that the routing DLL is configured properly. - Event ID: 12071 Event Type: Warning Event Source: MSExchangeIS Event Category: Content Engine Description: Message with subject from exceeded the maximum hop count(80040C02-8200008C). The archive filename is . - Event ID: 4098 Event Type: Error Event Source: MSExchangeIMC Event Category: Internal Processing Description: The following message could not be delivered because the hop count exceeded the maximum. Check your configuration to make sure messages are not looping. From: Subject: CAUSE ===== This behavior occurs because Internet Mail Service is connecting to itself in an attempt to deliver the message. It is important to note that this is not a problem with either Exchange Server or Windows 2000. Refer to the "More Information" section of this article for further explanation of this behavior. RESOLUTION ========== To resolve this problem, use one of the following methods: - Add an MX record for .com in DNS specifying the proper mail host. - Add .com in the "Specify by E-Mail Domain" area on the Connections tab of Internet Mail Service properties specifying the proper mail host. - On the Routing tab of Internet Mail Service, configure .com to route to the correct destination mail host. NOTE: The first two methods are the best ways to resolve this issue. Although the third method prevents the message from looping, it still causes Internet Mail Service to first connect to itself to deliver the message and then reroutes the message to its intended destination. MORE INFORMATION ================ When a Windows 2000 domain controller is created, it registers an A record for its Windows 2000 domain. In the situation described in this article, the Windows 2000 domain is .com. NOTE: This domain should not be confused with the domain used for Internet mail. The domain .com specifies a security namespace, while the domain .com specifies a messaging namespace. The two namespaces are completely separate, and can have different names. Therefore an A record for .com is dynamically registered in DNS, and it points to the IP address of the domain controller. When Internet Mail Service tries to deliver an SMTP message, the service first queries DNS for an MX record for the destination domain. If the query does not return an MX record for the destination domain, Internet Mail Service queries DNS for an A record for the destination domain. If an A record is returned, Internet Mail Service connects to the IP address specified in the A record and delivers the message. In this situation, Internet Mail Service attempts to deliver the message to itself because of the following reasons: - The MX record query does not return any records because an MX record is not configured in DNS. - The A record query successfully finds the A record for the domain controller. Additional query words: XMRP imc ====================================================================== Keywords : kberrmsg kbnetwork exc55 Technology : kbExchangeSearch kbExchange550 kbZNotKeyword2 Version : winnt:5.5 Issue type : kbprb ============================================================================= THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY. Copyright Microsoft Corporation 2002.