XADM: Exchange Sends Message Without Valid O/R Address

   show 100 percent CPU usage.

CAUSE

In a non-replicated environment, the Exchange MTA may not be able to resolve a recipient's distinguished name within the Exchange directory. Non- resolvable distinguished names result usually from invalid recipient entries in the personal address book (PAB) of a user. If there is an X.400 Connector with an address space of 'C=*' defined, the MTA may attempt to send a message destined for such a recipient via this connector. In doing so, the MTA does not generate a valid X.400 O/R address but uses the recipient's distinguished name as an X.400 directory name.

RESOLUTION

To resolve this problem, Exchange sites connected via an X.400 Connector with an address space of 'C=*' defined, should be configured as Connected Sites in the X.400 Connector's Connected Sites property page. If this resolution is not possible, obtain the following fix or wait for the next Exchange service pack.

STATUS

Microsoft has confirmed this to be a problem in Exchange Server versions 5.0 and 5.5. A supported fix for both versions is now available, but has not been fully regression-tested and should be applied only to systems experiencing this specific problem. Unless you are severely impacted by this specific problem, Microsoft recommends that you wait for the next Service Pack that contains this fix. Contact Microsoft Technical Support for more information.

MORE INFORMATION

All occurrences of the problem described here involve two or more non- replicated Exchange sites. Additionally, there must be a connector defined with the "catch-all" address space of 'C=*'.

For the above symptoms 2, association is hanging, and 3, MTA causes 100 percent CPU usage, an intermediate third-party X.400 system must be involved.

There are currently three known reasons for the existence of a distinguished name that cannot be resolved in a user's PAB:

1. A user has been moved to a different non-replicated Exchange site. During this move, the user kept his or her PAB containing recipients defined in the original site's directory. NOTE: Moving PABs to non-replicated sites is not supported.

2. A user has been deleted from the directory, but the user has the deleted recipient still as an entry in his or her PAB.

3. This scenario involves two Exchange Server computers, referred to as ServerA and ServerB in the following. It involves three Exchange users: UserSend, UserForward, and UserReceive. UserSend and UserForward are located on ServerA. UserReceive is located on ServerB.

   ServerA and ServerB are connected via an X.400 Connector. Both sides of the X.400 Connector have an address space defined that represents the other server's site addressing. ServerB has an additional X.400 Connector defined to either a third Exchange Server computer or a foreign X.400 MTA. The address space on that connector is defined as "C=*". The "X.400 bodypart used for message text" on the connector's Advanced property page must have different settings on both ends of the connector; for example, IA5 on ServerA and IA5 (German) on ServerB. UserSend sends a message to UserForward. UserForward sends a message to UserReceive, inserting the message received from UserSend as attachment to this message. When UserReceive opens the attached message, UserReceive will be able to add UserSend to his or her PAB. Viewing the just added e-mail address, it will be evident that it is a pure distinguished name. This distinguished name cannot be resolved within ServerB's directory.