Event ID - 201

Event Id201
DescriptionA loop has been detected in the message message. being transferred in. A non-delivery report was generated with reason code unable-to-transfer and diagnostic code loop-detected. [MTA XFER-IN 11 104] (14)
Event InformationAccording to Microsoft:
This problem occurs if all the following conditions are true:
1. You have X.400 connectors configured between your Exchange 5.5 site and your Exchange 2000 or Exchange 2003 administrative group.
2. A mail-enabled distribution group is created in the Exchange 2000 or Exchange 2003 administrative group.
3. The mail-enabled distribution group contains an X.400 contact whose address corresponds to the X.400 address of a recipient in your Exchange 5.5 site.
4. An expansion server is not specified in the Exchange 2000 or Exchange 2003 administrative group for the mail-enabled distribution group.
To resolve this problem, use one of the following methods:
1. Specify an expansion server for the mail-enabled distribution group. When you specify an expansion server, the message categorizer removes trace information from the message that is sent over the X.400 connector.
2. Expand the distribution list locally on the Exchange 5.5 computer that the message is sent from.
Reference LinksYou receive a non-delivery report when you send a message from an Exchange Server 5.5 computer to a distribution group that is hosted in a mixed administrative group

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