Configuring Message Routing

Configuring Message Routing

Microsoft Exchange 2000 Server is designed to serve companies of all sizes. Smaller companies can meet all of their messaging and collaboration needs using a single computer running Exchange. Larger companies may require more complex configurations, with connections between multiple computers running Exchange or between Exchange and other messaging systems.

An Exchange mail system, or organization, consists of one or more computers, or servers, on which Exchange is installed. In all but the smallest Exchange installations, you will likely need to configure multiple computers running Exchange to work together. Within some groups of computers, servers are connected by reliable, permanent connections. Groups of servers linked together in this way are called a routing group. Between routing groups, connections may be unreliable or slower.

Routing group configuration becomes necessary only when you need to connect two or more routing groups or when you install connectors to foreign messaging systems in your Exchange installation. Communication between routing groups is handled by Exchange Routing Group connectors.

For information on planning your messaging system, see Microsoft Exchange 2000 Server Planning and Installation. After you determine the topology for your messaging system, the topics in this section provide the background information you need to connect computers running Exchange and to understand how messages are routed from one computer to another.

Note   If you are operating Exchange on a single server, the topics in this section do not apply to your organization; however, you may find these topics useful for any planning you need to do to expand your messaging network to multiple servers.

Note   You can add servers to routing groups only during installation. By default, every server in your organization is added to a routing group. After installation, you can move servers between routing groups to put servers with reliable connections in the same routing group.

For help with specific tasks, see How To.

For general information, see Concepts.

Answers to Frequently Asked Questions

What is the difference between an administrative group and a routing group in Exchange 2000?

In Exchange 2000, an administrative group is a collection of Exchange servers and configuration objects that are grouped together for a common administrative purpose. A typical reason for creating an administrative group is to define a unit of access control; for example, if your organization has two sets of administrators that manage two sets of Exchange servers, you can create two administrative groups, each containing one set of servers. A routing group is a set of Exchange servers with full-time, reliable connections that communicate with each other directly.

How do administrative groups and routing groups work in an Exchange 2000 Server installation that is in mixed mode?

In Exchange Server 5.x, administration is based on sites that contain both routing and administrative information. When Exchange 2000 Server is in mixed mode, in which Exchange 2000 servers coexist with Exchange 5.x servers, the same relationship between administration and routing exists. The Exchange 2000 administrative group and routing group are coupled, and there is only one routing group for each administrative group.

How do administrative groups and routing groups work in an Exchange 2000 Server installation that is in native mode?

When an Exchange organization is in native mode, all Exchange servers are running Exchange 2000 Server, and administrative groups and routing groups can be configured separately. Servers and connectors can be grouped together into one or more administrative groups, or they can be separated into different groups by function. A server can belong to an administrative group for management purposes but does not have to belong to one of the routing groups within that administrative group. For example, you can create a single administrative group to hold all routing groups within your organization and create other administrative groups for the daily administration of the rest of the Exchange objects.

How does routing work in Exchange 2000?

The server looks up the recipient in the Active Directory and the routing engine calculates the lowest cost route. The routing engine directs mail messages to the next server in the route using one of the available connectors. It also takes into consideration any restrictions that may apply, such as user restrictions or message size. Connector costs range between one and 100 and are assigned per address space. A connector cost represents the preference for one connector over others. Since a connector can support multiple address spaces, it may be associated with several costs.

Should I have one or more than one bridgehead server in a routing group?

If you want all mail to flow through one computer to track or archive messages, designate a single bridgehead server. If your mail traffic is light and if you have a bridgehead server that is likely to be up at all times, a single bridgehead server is adequate. You need multiple bridgehead servers for load balancing if you have heavy mail traffic, and for fault tolerance if a bridgehead server fails.

Why are Routing Group connectors preferred over SMTP and X.400 connectors?

Routing Group connectors are simpler to use because they have few parameters to configure. When you connect two Routing Group connectors, the connection works automatically and reliably. With SMTP and X.400, you need to make sure the connector is configured correctly at the source and destination; however, you can use Routing Group connectors only to connect routing groups. They cannot connect a routing group to a foreign mail system.

When should I use an SMTP connector?

Although Routing Group connectors are easier to configure, an SMTP connector offers capabilities that are unavailable with a Routing Group connector. SMTP connectors allow you to connect to foreign mail systems or SMTP hosts on the Internet, designate a smart host, enable custom authentication and encryption for the connection, specify remotely triggered mail delivery, and set message size limits.

When should I use an X.400 connector?

Generally, you use an X.400 connector only to connect to existing X.400 mail systems.

How many connectors can I have in a routing group?

You can create as many connectors as you want in a routing group and have as many connectors as you want on a single server. Each X.400 connector can only have a single local bridgehead server and a single remote bridgehead server. SMTP connectors can have multiple local bridgehead servers and multiple smart hosts (separated by semi-colons). For load balancing, however, Microsoft recommends using a single SMTP connector configured with multiple smart hosts and/or multiple local bridgeheads. Load balancing with X.400 connectors can only be achieved with multiple connectors. You may also want to configure multiple X.400 connectors to support different transport types, such as TCP/IP or X.25.