Active Directory sites are not managed by Exchange administrators. You must have the permissions assigned to the Active Directory Enterprise Administrators group to create, delete, or modify Active Directory sites. However, because the Exchange routing topology is derived from the Active Directory site topology, an Exchange administrator can apply an Exchange-only attribute to an Active Directory site that is considered only by Exchange 2007 routing.

In your Exchange organization you may have to force all message delivery to be relayed through a particular Active Directory site. In this scenario, connectivity may prevent direct SMTP relay between sites. Therefore, messages must be relayed through an interim site before they are sent to their destination. Because of an Exchange organization's internal policies, an administrator may also want to relay all messages through a particular site. You can use Exchange Management Shell tasks to designate an Active Directory site as a hub site.

You use the Set-ADSite cmdlet to specify an Active Directory site as a hub site. Whenever a hub site exists along the least cost routing path for message delivery, the messages queue and are processed by the Hub Transport servers in the hub site before they are relayed to their ultimate destination. When an Active Directory site is configured as a hub site, routing paths that include that site are always relayed through the hub site.

For more information, see the following topics:

• Set-AdSite
  
• How to Configure a Hub Site
  

Like Active Directory sites, Active Directory IP site links are not managed by Exchange administrators. You must have the permissions assigned to the Active Directory Enterprise Administrators group to create, delete, or modify Active Directory site links. However, because the Exchange routing topology is derived from the Active Directory site topology, an Exchange administrator can apply an Exchange-only attribute to an Active Directory site link that is considered only by Exchange 2007 routing.

By default, Microsoft Exchange uses the cost assigned to an IP site link for Active Directory replication purposes to compute a routing topology. If, after documenting the existing Active Directory site and IP site link topology, you verify that the link costs for the Active Directory site and the network traffic flow patterns are not optimal for Exchange 2007, you can make adjustments to the costs evaluated by Microsoft Exchange. As an Exchange administrator, you cannot and should not modify the cost assigned to the IP site link by using Active Directory tools. Instead, use the Set-ADSiteLink cmdlet in the Exchange Management Shell to assign an Exchange-specific cost to the IP site link.

When an Exchange cost is assigned to an IP site link, the Exchange cost overrides the Active Directory cost for message routing purposes. Routing only considers the Exchange cost when it evaluates the least cost routing path.

New in Exchange 2007 Service Pack 1

Exchange 2007 transport servers require Send connectors to deliver messages to the next hop on the way to their destination. A Send connector controls outbound connections from the sending server to the receiving server or destination e-mail system. The address space for a Send connector specifies the following conditions:

• The recipient domains to which this connector routes e-mail
  
• The transport type
  
• The cost assigned to that address space on that particular Send connector
  

By default, no explicit Send connectors are created when the Hub Transport server role or the Edge Transport server role is installed. However, the implicit intra-organization Send connector is used to route messages internally. End-to-end mail flow is only possible if one of the following conditions is true:

• You have subscribed the Edge Transport server to the Active Directory site by using the Edge Subscription process.
  
• You have manually configured Send connectors and Receive connectors to route Internet mail.
  

By default, protocol logging for the intra-organization Send connector is disabled. You can enable or disable protocol logging for the intra-organization Send connector by using the Set-TransportServer cmdlet.

For more information, see the following topics:

• Send Connectors
  
• Set-TransportServer
  
• Managing Protocol Logging
  
• How to Configure Connectors for Internet Mail Flow
  

If Exchange 2007 and Exchange 2003 or Exchange 2000 coexist in the same organization, you must configure routing group connectors between the single, global Exchange 2007 routing group and the routing groups configured in the earlier version of Exchange Server. The first routing group connector between Exchange 2007 and Exchange 2003 or Exchange 2000 is created and configured during installation of the first Hub Transport Server role in an existing Exchange organization.

You must use the Exchange Management Shell to configure routing group connectors that include an Exchange 2007 Hub Transport server as either a source server or target server. To support coexistence with Exchange 2003 and Exchange 2000, all computers that are running Exchange 2007 are automatically put into a single routing group when the first Hub Transport server role is installed. The routing group in Exchange 2007 is recognized in the Exchange System Manager of Exchange 2003 and Exchange 2000 as Exchange Routing Group (DWBGZMFD01QNBJR). You cannot use the Exchange System Manager of Exchange 2003 and Exchange 2000 to manage the Exchange 2007 routing group or any routing group connectors that include an Exchange 2007 Hub Transport server as either a source server or target server.

New in Exchange 2007 SP1

Exchange 2007 provides tools and extensive logging resources to help you with mail flow problems. The following diagnostic tools are available in the Toolbox of the Exchange Management Console:

• Exchange Server Best Practices Analyzer   Use the Best Practices Analyzer to check the configuration and health of the Exchange topology. This tool automatically gathers and examines information about the configuration of the Exchange organization and summarizes the findings in a report. The report lists problems by severity and includes a suggested fix for the issue. Additionally, this tool provides a list of recent changes and a detailed summary of the Exchange organization configuration. For more information, see Microsoft Exchange Analyzers.
  
• Exchange Mail Flow Troubleshooter   Use the Exchange Mail Flow Troubleshooter tool to help diagnose mail flow and transport-related problems. This tool lets you select a mail flow symptom, analyzes your configuration, and outputs findings to a report. For more information, see Overview: Microsoft Exchange Analyzers.
  
• Message Tracking   Use the Message Tracking tool to examine the contents of message tracking logs. For more information, see Managing Message Tracking.
  
• Queue Viewer   Use the Exchange Queue Viewer to view and manage Exchange mail queues. For more information, see Using the Queue Viewer to Manage Queues.
  

New in Exchange 2007 SP1

For more information, see the following topics:

• Planning to Use Active Directory Sites for Routing Mail
  
• Understanding Active Directory Site-Based Routing
  
• Managing Connectors
  
• Coexisting with Exchange Server 2003 and Exchange 2000 Server
  
• Message Routing in a Coexistence Environment
  
• Managing Message Tracking
  
• Managing Queues
  
• Managing Message Size Limits