Public folder replication issues that occur after you install Exchange 2007 in an existing Exchange 2003 organization

• The users who log on to the Exchange 2007 mailboxes cannot view the Exchange 2003 public folders through a Microsoft Outlook client.
• On the Exchange 2003-based server, the public folder replication messages are queued in the "messages together with an unreachable destination" queue.
• The following event log is logged on the Exchange 2003-based server:

  Event Type: Warning
  Event Source: MSExchangeTransport
  Event Category: Routing Engine/Service
  Event ID: 951
  Description: When sending mail to following address exchange2007name.domain.com.5B2DCAE3-0882-1148-8DEB-B36F641F9E2B, we have found the connector with target domain *.5B2DCAE3-0882-1148-8DEB-B36F641F9E2B matching destination address exists in DS. However, we have no way of getting there. Possibly, you need to check your topology and add appropriate connectors among Routing Groups.

• You install Exchange 2007 with only the mailbox role enabled.
• You install Exchange 2007 with the hub transport role. You do not select an Exchange 2003 or an Exchange 2000 routing group connector bridge head server. Therefore, there is no routing group connector between the default routing groups in Exchange 2007 and Exchange 2000 or between the default routing groups in Exchange 2007 and Exchange 2003.
  
  Note The first routing group connector between Exchange 2007 and Exchange 2003 or between Exchange 2007 and Exchange 2000 is created and configured when the first hub transport server role is installed in an existing Exchange organization.

• If you have not installed the Exchange 2007 hub transport role to the existing Exchange 2003 organization, install the Exchange 2007 hub transport server to the organization. Do not forget to select a routing group connector bridge head server during installation.
• If you have installed Exchange 2007 hub transport role but forgot to select a routing group connector bridge head server, use Exchange Management Shell to manually create the routing group connector.

New-RoutingGroupConnector -Name "Interop RGC" -SourceTransportServers "Ex2007Hub1.contoso.com" -
TargetTransportServers "Ex2003BH1.contoso.com" -Cost 100 -Bidirectional $true -PublicFolderReferralsEnabled $true

Steps to reproduce this problem

1. Install Exchange 2007 with the mailbox role and with the Hub transport role to the existing Exchange 2003 organization.
2. Do not select an Exchange 2000 or an Exchange 2003 routing group connector bridge head server during installation.
3. After installation is complete, verify that there is no routing group connector between Exchange 2007 routing groups and Exchange 2003 routing groups.
4. Try to replicate the public folders from Exchange 2003 to Exchange 2007.