DOCUMENT:Q187915  07-MAY-1999  [exchange]
TITLE   :XCON: MTA Routes Mail to EDK Connector when Other Route Exists
PRODUCT :Microsoft Exchange
PROD/VER:WinNT:5.5
OPER/SYS:
KEYWORDS:exc55sp2fix

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The information in this article applies to:

 - Microsoft Exchange Server, version 5.5 
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SYMPTOMS
========

If an Exchange Development Kit (EDK) Connector is installed on an Exchange
Server 5.5 computer, and the EDK Connector has the same address space as another
Exchange connector, the Exchange message transfer agent (MTA) will possibly
route messages incorrectly to the EDK Connector.

MORE INFORMATION
================

For example, a company develops an EDK Connector that can handle X.400
addressing schemes. This company also has to send X.400 mail out an X.400
Connector. This is not a problem if the address spaces are different. But if the
same message handling capability is needed for both connectors, this presents a
problem.

On a typical X.400 Connector for an entire organization, the address space is
X400:c=*. If both connectors have c=*, it is possible for messages that are
meant for the EDK Connector to be routed out the X.400 Connector, resulting in a
non-delivery report (NDR). The problem is also manifested by incoming messages
from the EDK Connector into Exchange. If the message coming into Exchange is
routed right back to the EDK Connector, an NDR will be generated if the message
travels out the X.400 Connector.

Microsoft has changed the behavior of the Exchange MTA in Exchange Server version
5.5 Service Pack 2. The MTA now checks to see which connector the message
originated from. If there is a duplicate route that is equally weighted in all
categories, the MTA tries the duplicate route rather than sending the message
back to the originating EDK Connector.

RESOLUTION
==========

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

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


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 2.


Additional query words: routing route EMSMTA routes
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Keywords          : exc55sp2fix 
Technology        : kbExchangeSearch kbExchange550 kbZNotKeyword2
Version           : WinNT:5.5
Issue type        : kbbug
Solution Type     : kbfix

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