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
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
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
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.
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
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.
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.
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.
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.