Q251441: XIMS: Internet Mail Service NDR Behavior Changes in 5.5 SP3

Article: Q251441
Product(s): Microsoft Exchange
Version(s): winnt:5.5 SP3
Operating System(s): 
Keyword(s): exc55sp3
Last Modified: 05-FEB-2000

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The information in this article applies to:

- Microsoft Exchange Server, version 5.5 SP3 
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SUMMARY
=======

The From address of the postmaster in the non-delivery report (NDR) is different
from the e-mail domain that the original in-bound message was destined to. This
difference may occur if the Internet Mail Service returns the NDR through
another Internet Mail Service. Such new behavior is a result of the "Bounce
Back" feature in the Microsoft Exchange Server message transfer agent (MTA).

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

The Bounce Back feature is meant to eliminate the message looping by reducing
the possibility of an MTA sending a message to a route that was already taken by
a message. This feature also changes the way the MTA routes an NDR message that
would have been sent out of the local Internet Mail Service. This feature was
first applied as a post-Service Pack 2 (SP2) fix and then was rolled into
Exchange Server 5.5 Service Pack 3 (SP3) where it is the default algorithm.
Consequently, an Internet Mail Service NDR message takes a route different than
the path taken by the original message when there are several routes available.

The Bounce Back feature can be turned off by installing SP3 and setting the Only
Use Least Cost Routes option. To locate this option

1. In the Microsoft Exchange Server Administrator program, click Organization,
  click Site, click Configuration, click Servers, and then double-click your
  server.

2. In the MTA Properties dialog box, click the General tab.

By implementing the fix, the MTA handles NDR replies by causing the NDR to be
routed back along the lowest cost route for its address space (which is the
local connector). In essence, the NDR routes back along the same path of the
original message that produced the NDR.

A further consequence of this new MTA routing feature is that a message coming in
one Internet Mail Service that produces an NDR that goes out a second Internet
Mail Service will have the From address of the second Internet Mail Service
postmaster, which might be a different e-mail domain than the e-mail domain to
which the original in-bound message was destined. This can be confusing to the
recipient of the NDR.


Additional query words: IMC XFOR XCON IMS

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Keywords          : exc55sp3 
Technology        : kbExchangeSearch kbZNotKeyword2 kbExchange550SP3
Version           : winnt:5.5 SP3
Issue type        : kbinfo

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