Microsoft Exchange 2000 Server can connect to a multitude of modern and legacy messaging systems. Until this point, we have focused primarily on working within the Microsoft Exchange 2000 Server environment. You have set up your Exchange system and learned how to deploy and administer all of its components—from routing groups to clients to clustered servers. Exchange 2000 Server is not the only messaging system out there, however. Many types of messaging systems are available today, and you may have to connect your Exchange system to one or more of them. You may, for example, be upgrading from a legacy system or need to establish communications with another company. This chapter covers the basics of connecting Exchange 2000 Server to other messaging systems, referred to as foreign systems.