XCON: Messages to Custom Recipients Are Undeliverable After You Apply SP1

After you apply Exchange Server 5.5 Service Pack 1 (SP1), messages that you send to Fenestrae Faxination custom recipients are returned as undeliverable by the message transfer agent (MTA) with the following non-delivery report: The MTA also records the following event: Additional notes about this problem:

�	This problem cannot be reproduced with the original release of Exchange Server 5.5.
�	This problem cannot be reproduced if Exchange Server 5.5 Service Pack 2 (SP2) or later is applied without first installing SP1.
�	When you apply SP2 or later, the problem is not resolved.

This problem may be caused by the lack of an X.400 proxy address for the custom recipients.

To resolve this problem, add an X.400 proxy address for all custom recipients. You can do this manually in the Exchange Administration program or programmatically by using a variety of tools.

Exchange Server versions 4.0 through 5.5 are all X.400-based, and the routing of messages depends heavily on X.400 addresses. It is not typical that an Exchange Server-based computer routes messages to objects without X.400 proxy addresses, but it is typical that an Exchange Server-based computer returns such messages as undeliverable.

To illustrate the importance of the X.400 proxy address, administrators may locate the Site Addressing object in the Configuration container of any site, and then click the Site Addressing tab in properties. If the administrator attempts to clear the X.400 E-mail address, the administrator receives the following error message: There is no way to remove or disable the X.400 site proxy address. However, the Exchange Server-based computer does allow administrators to remove X.400 proxy addresses for recipients, custom recipients, and distribution lists, and the administrator does not receive any warning messages when they do this. Administrators are therefore cautioned to only remove proxy addresses when they are fully aware of the implications of that action.