The following tasks must be performed before setting up advanced security for a mailbox and a site:
You install KM server using the Complete/Custom option in the Microsoft Exchange Server Setup program.
The KM server uses the Microsoft Certificate Server computer to certify public signing and encryption keys. Before installing Microsoft Certificate Server, you must have successfully installed Microsoft Internet Information Server (IIS) version 4.0 on a computer running Microsoft Windows NT Server version 4.0. Once installation of Microsoft Certificate Server is complete, you must install the Exchange policy module before the Microsoft Certificate Server computer can be used by KM server. The Exchange policy module enables the Microsoft Certificate Server computer to evaluate, accept, and issue certificate requests.
For more information on installing KM server, and setting up Microsoft Certificate Server and an Exchange policy module, see Microsoft Exchange Server Getting Started.