Exchange System Manager is an MMC-based tool that provides administrators with a graphical user interface for managing the configuration of Exchange 2000 Server or Exchange Server 2003 organizations. Administrators of Exchange 2000 and earlier versions will be able to take advantage of Exchange 2003 ESM as soon as the first Exchange 2003 server is added to their organization. The caveat is that the administrators must run the ForestPrep procedure before using the Exchange 2003 ESM or when using the tool in a non-Microsoft supported environment.
Using ESM 2003 in mixed mode environments is supported; however, certain restrictions and limitations exist. As you know, Exchange System Manager 2003 can manage Exchange 2003, Exchange 2000, and Exchange 5.5 servers. Exchange System Manager 2003 cannot manage any components that existed in Exchange 2000 but that were removed from Exchange 2003, such as Key Management Service, Instant Messaging and Chat, or legacy connectors. Because these components are not supported, they will not appear in the ESM console. New Exchange features such as Queue Viewer, Move Mailbox, Mailbox Recovery Center, and Internet Mail Wizard can all be used in Exchange 2000 and Exchange 2003 environments.
There are a few things that administrators should remember: