You 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

Your message did not reach some or all of the intended recipients.

      Subject:	<subjectname>
      Sent:	<date and time>

The following recipient(s) could not be reached:

      <recipientName> on <date and time>
            A configuration error in the e-mail system caused the message to bounce between two servers or to be forwarded between two recipients.

Event 1

Event Type: Warning
Event Source: MSExchangeMTA
Event Category: X.400 Service
Event ID: 290
Description: A non-delivery report (reason code unable-to-transfer and diagnostic code loop-detected) is being generated for message message. It was originally destined for recipient (recipient number 1), and was to be redirected to . [MTA DISP:ROUTER 12 136] (12)

Event 2

Event Type: Warning
Event Source: MSExchangeMTA
Event Category: X.400 Service
Event ID: 201
Description: A 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)

• You have X.400 connectors configured between your Exchange 5.5 site and your Exchange 2000 or Exchange 2003 administrative group.
• A mail-enabled distribution group is created in the Exchange 2000 or Exchange 2003 administrative group.
• 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.
• An expansion server is not specified in the Exchange 2000 or Exchange 2003 administrative group for the mail-enabled distribution group.

1. The Exchange 5.5 user sends a message to the mail-enabled distribution group that is hosted on the Exchange 2000 or Exchange 2003 computer.
2. This message travels over the X.400 connector to the Exchange 2000 or Exchange 2003 organization.
3. The mail-enabled distribution group is expanded on an Exchange 2000 or Exchange 2003 computer.
4. The message is delivered successfully to the local administrative group users.
5. A message is sent back through the same X.400 connector to the Exchange 5.5 contact who is specified in the distribution group.
6. The Exchange 5.5 computer generates an NDR delivery status notification because it determines that the message is looping.

Method 1

1. Start the Active Directory Users and Computers tool.
2. On the View menu, click Advanced Features.
3. Locate the distribution group that you want to modify.
4. Right-click the distribution group, and then click Properties.
5. Click the Exchange Advanced tab, and then click an Exchange Server computer in the Expansion server list.
6. Click OK.

Method 2

1. Start the Microsoft Exchange Administrator tool.
2. Expand Configuration, expand Servers, expand your Exchange Server computer, and then click Message Transfer Agent in the right pane.
3. On the File menu, click Properties.
4. On the General tab, click to select the Expand remote distribution lists locally check box, and then click OK.

• When the message is sent to a distribution group and an expansion server is specified.
• When message journaling is enabled.
• When the message is sent to a public folder.