Exchange 2000 sub-systems, such as protocol, storage, and directory features, can be placed on different servers to improve scalability. For example, you can configure Exchange 2000 topology to consist of a bank of front-end and back-end servers, enabling users to connect to virtual Internet Protocol (IP)-addressable front-end servers while storing messages and collaboration data on separate back-end servers.

You can build large public e-mail systems by separating components onto different servers. This increases reliability because a failure on one server will not affect the other components. For example, you can host a set of protocol servers separately without Redundant Array of Inexpensive Disks (RAID) controllers to reduce cost and prevent protocol failures from affecting Web Storage System or Active Directory. Because Exchange 2000 doesn't require that you host directory services on each computer, you have more flexibility in your deployment.

Note MAPI clients, such as Microsoft Outlook 97, Microsoft Outlook 98, and Microsoft Outlook 2000 clients working in a "Corporate Workgroup" mode, cannot use a front-end server; they must always use the back-end server.