Applies to: Exchange Server 2007 SP1, Exchange Server 2007
Topic Last Modified: 2007-07-16

This topic provides information about how to troubleshoot mail flow between servers that are running Microsoft Exchange Server 2003 or Exchange 2000 Server and an Exchange Server 2007 Hub Transport server. This problem occurs when you have deployed at least one Exchange 2007 Hub Transport server in an existing Exchange organization. When you try to send messages between the two mail systems, the messages are put in the Unreachable queue on the Hub Transport server or in the Messages with an unreachable destination queue on an Exchange 2003 or Exchange 2000 server.

This problem can occur when no routing group connector is created during the installation of the first Hub Transport server in an existing organization. A routing group connector is required for mail flow between Exchange 2007 and Exchange 2003 or Exchange 2000. During setup, two routing group connectors are automatically created to enable mail flow in both directions. If you use the Setup wizard, select an Exchange 2003 or Exchange 2000 bridgehead server to act as the source server for one routing group connector and as the target server for the reciprocal connector. If you use Setup.com to perform an unattended installation, you must provide the /legacyroutingserver parameter to automatically create the required routing group connectors. If you do not perform this procedure during setup of the first Hub Transport server, the two e-mail systems cannot determine a route between them. Messages that are sent from users with mailboxes located on Exchange 2003 or Exchange 2000 servers to recipients with mailboxes located on Exchange 2007 Mailbox servers are put in the Messages with an unreachable destination queue on an Exchange 2003 or Exchange 2000 server. Messages that are sent from users with mailboxes located on Exchange 2007 Mailbox servers to recipients with mailboxes located on Exchange 2003 or Exchange 2000 servers will queue in the Unreachable queue on the Exchange 2007 Hub Transport server. For more information about how to install Exchange 2007 in an existing Exchange organization, see How to Install Exchange 2007 in an Existing Exchange Server 2003 Organization.

The Unreachable queue is a persistent queue that contains messages that cannot be routed to their destinations. Microsoft Exchange can resolve and locate the recipient. But Microsoft Exchange can't determine how to reach the destination. The messages remain in the Unreachable queue until they expire or until the administrator resubmits the messages to the categorizer. For more information about how to resubmit messages in the Unreachable queue, see How to Resubmit Messages in Queues.

To resolve this problem, you must create the required routing group connectors. You can't use Exchange System Manager on the server that runs Exchange 2003 or Exchange 2000 to perform this procedure. You must use the Exchange Management Shell on the Exchange 2007 server.

Before You Begin

To perform this procedure, the account you use must be delegated the following:

  • Exchange Organization Administrator role

For more information about permissions, delegating roles, and the rights that are required to administer Exchange 2007, see Permission Considerations.

Procedure

To use the Exchange Management Shell to create routing group connectors

  1. Run the following command to create a routing group connector from Exchange 2007 to Exchange 2003 or Exchange 2000 and to automatically create the reciprocal routing group connector. This command sets the routing group connector cost as 10 and enables public folder referrals between the two versions of Exchange Server:

    Copy Code 
    New-RoutingGroupConnector -Name "Interop RGC" -SourceTransportServers "Ex2007Hub1.contoso.com" -TargetTransportServers "Ex2003BH1.contoso.com" -Cost 10 -Bidirectional $true -PublicFolderReferralsEnabled $true

  2. Run the following command to verify that the two routing group connectors are created:

    Copy Code 
    Get-RoutingGroupConnector

For detailed syntax and parameter information, see Routing Group Connector Cmdlets.

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