As I wrote previously, Exchange 2003 is a more focused version of Exchange. The collaborative features introduced in Exchange 2000 have been removed, producing a new identity for Exchange—one that takes it back to its core of messaging. This section is primarily for Exchange 2000 administrators who are planning or considering an upgrade to Exchange 2003. It details the components and technologies that have been retired or deprecated in Exchange 2003. In some cases, Microsoft offers or will soon offer replacement technology for some of the missing features; in other cases, no replacement or substitute is available. I'll start with the most prominent changes and work down to some minor things that have been removed.