XIMS: The Internet Mail Service Non-Delivery Report Behavior Changes in Exchange Server 5.5 SP3 (251441)

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.