A. When you install your first Exchange 2003 server in an Exchange 5.5 organization, the installation wizard asks you which Exchange 5.5 server you want to connect to. After you've specified an Exchange 5.5 server to connect to, the Exchange 2003 server is added to the administrative group that matches the site name that the Exchange 5.5 server to which you're currently connected belongs to. Exchange 2003 creates an administrative group during your organization's first Exchange 2003 server installation for each existing Exchange 5.5 site.
When you install the next Exchange 2003 server, the wizard displays a selection of existing administrative groups from which you can choose a group for the new server. For example, if you have three Exchange 5.5 sites, siteA, siteB, and siteC, after you install the first Exchange 2003 server, Exchange 2003 creates three administrative groups--siteA, siteB, and siteC.