Which Proxy feature must be installed to configure a computer running Windows Server 2008 as the RPC proxy server?

In a scenario where you want to configure a computer running Windows Server 2008 as an RPC proxy server, the key feature that must be installed is RPC over HTTP. This specific feature enables the exchange of Remote Procedure Call (RPC) requests over HTTP, enhancing connectivity in environments that use Microsoft Exchange.

When installed, RPC over HTTP facilitates secure communication between Outlook clients and Exchange servers through the usage of HTTP or HTTPS protocols, allowing for greater support in scenarios involving firewalls or networks that restrict specific ports. This capability is essential for enabling users to connect to Exchange services remotely, especially when their Outlook clients are behind strict firewall rules or in different network segments.

The other options do not specifically relate to the configuration of a Windows Server 2008 computer as an RPC proxy server. While HTTP Proxy and other proxies might offer general proxy capabilities, they do not provide the specific functionalities needed for RPC communications within the context of Microsoft Exchange. Thus, for this kind of setup, RPC over HTTP stands out as the critical feature necessary to ensure interoperability and efficient routing of communications between clients and servers.