DOCUMENT:Q232586  30-SEP-1999  [exchange]
TITLE   :XCON: X.400 MTA Logs "Loop Detected" Error Message
PRODUCT :Microsoft Exchange
PROD/VER:winnt:5.5
OPER/SYS:
KEYWORDS:exc55 EXC55SP3Fix

======================================================================
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The information in this article applies to:

 - Microsoft Exchange Server, version 5.5 
-------------------------------------------------------------------------------


SYMPTOMS
========

In some cases, a third-party X.400 message transfer agent (MTA) may log an error
message similar to "Loop detected" when it receives a message from Exchange
Server. The originator of the message will receive a non-delivery report (NDR).

This behavior only occurs under very specific circumstances:

 - A message is sent from Exchange Server using the X.400 Connector. The
   recipients in the message are taken from the user's Personal Address Book
   (PAB) or are one-off addresses. At the same time, custom recipients exist for
   these addresses in the Exchange Server global address list.

 - The message may contain multiple trace records in the X.400 P1 message
   header, which are marked as "rerouted." This may cause the receiving MTA to
   think there is a message loop.

 - The number of trace records in the P1 message header depends on the number of
   recipients addressed. For example, if the message was sent to three
   recipients, there will be three trace records.

RESOLUTION
==========

To resolve this problem, obtain the latest service pack for Exchange Server
version 5.5. For additional information, please see the following article in the
Microsoft Knowledge Base:

   Q191014 XGEN: How to Obtain the Latest Exchange Server 5.5 Service Pack

The English version of this fix should have the following file attributes or
later:

Component: Message Transfer Agent (MTA)

+---------------------------+
| File name    | Version    | 
+---------------------------+
| Dbserver.sch | N/A        | 
+---------------------------+
| Dcprods.cat  | N/A        | 
+---------------------------+
| Ems_rid.dll  | 5.5.2621.0 | 
+---------------------------+
| Emsmta.exe   | 5.5.2621.0 | 
+---------------------------+
| Info4log.cfg | N/A        | 
+---------------------------+
| Infoblog.cfg | N/A        | 
+---------------------------+
| Infodlog.cfg | N/A        | 
+---------------------------+
| Infollog.cfg | N/A        | 
+---------------------------+
| Infoplog.cfg | N/A        | 
+---------------------------+
| Infotlog.cfg | N/A        | 
+---------------------------+
| Mtacheck.exe | 5.5.2621.0 | 
+---------------------------+
| Mtamsg.dll   | 5.5.2621.0 | 
+---------------------------+
| P2.xv2       | N/A        | 
+---------------------------+
| X400om.dll   | 5.5.2621.0 | 
+---------------------------+
| X400omv1.dll | 5.5.2621.0 | 
+---------------------------+



STATUS
======

Microsoft has confirmed this to be a problem in Microsoft Exchange Server
version 5.5. This problem was first corrected in Exchange Server 5.5 Service
Pack 3.

Additional query words: word-wrap truncated deleted

======================================================================
Keywords          : exc55 EXC55SP3Fix 
Technology        : kbExchangeSearch kbExchange550 kbZNotKeyword2
Version           : winnt:5.5
Issue type        : kbbug
Solution Type     : kbfix

=============================================================================

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