Why This Chapter Matters

When organizations install Exchange Server 2003, they do so in one of the following scenarios:

• Installing Exchange Server 2003 as a new installation in an organization with no previous mail system (most typical for a new organization).

• Migrating to Exchange Server 2003 from another mail system such as Lotus Notes or Novell GroupWise.

• Upgrading to Exchange Server 2003 from a previous version of Exchange Server.

• Installing Exchange Server 2003 to coexist with a previous version of Exchange Server.

The last three scenarios are the most common deployments of Exchange Server 2003 and are the focus of this chapter and of Chapter 5, "Migrating from Microsoft Exchange Server and Other Mail Systems."

This chapter focuses on preparing Exchange Server 5.5 to coexist with Exchange Server 2003 and installing Exchange Server 2003 into an existing Exchange Server 5.5 organization. Before you can install Exchange Server 2003 to coexist with Exchange Server 5.5, you must first connect Exchange Server 5.5 to Active Directory directory service. In this chapter, you will learn how to do that, as well as how to share information between Exchange Server 2003 and Exchange Server 5.5.