Summary

In this chapter, you learned how to use the tools that enable Exchange Server 2003 and previous versions of Exchange Server to coexist in the same organization. An organization running multiple versions of Exchange Server is referred to as running in mixed mode. An organization running only Exchange Server 2003 is referred to as running in native mode. Exchange Server 2003 operates in mixed mode by default, even if you have no previous versions running on your network. Once you switch to native mode, you cannot go back, and direct interoperability with previous Exchange versions is lost.

The primary advantage of running in mixed mode is that you can continue to use previous versions of Exchange (and any connectors and software specific to those versions) while upgrading your organization to Exchange Server 2003. There are also some limitations imposed by running in mixed mode. Exchange 5. x sites are mapped directly to Exchange Server 2003 administrative groups, meaning that administrative groups lose some of their flexibility. You also cannot move mailboxes between administrative groups when running a mixed-mode organization.

The primary components used in supporting mixed-mode operations are the Site Replication Service (SRS) and the Active Directory Connector (ADC). The SRS runs on an Exchange Server 2003 server and actually simulates an Exchange 5. x system from the viewpoint of the Exchange 5. x servers in a site. The ADC runs on an Exchange Server 2003 server and synchronizes directory information between Active Directory and Exchange 5. x servers in the site. ADC also synchronizes configuration information with those servers using the SRS as an intermediary. Only one instance of the ADC can run on a single Exchange server, but you can configure multiple connection agreements for an ADC. Each connection agreement is defined to replicate certain directory objects to certain parts of the Active Directory.

Once replication of directories is established, management of a mixed-mode organization is fairly straightforward. You can use Active Directory Users and Computers to manage all users from both Exchange Server 2003 and Exchange 5. x , although you can continue to manage users from System Administrator should you choose. Exchange Server 2003 servers and other Exchange Server 2003 ‚ specific configuration are managed through System Manager. Exchange 5. x ‚ specific configuration must be managed using System Administrator.