A. Actually, there are at least two tools. You can download Exchange Server Topology Diagramming Tool from the Microsoft Exchange Server Web site. This tool reads a Microsoft Exchange Server organization's directory using Active Data Objects (ADO) and turns the directory into a Visio 5.0 diagram showing sites, servers, and connectors. That's all it does, but it's free and includes source code you can customize to meet your needs.
Another document you can use is a commercial tool called Documentor from theecoraWeb site. Documentor automatically generates documentation of your Exchange and Windows NT architecture and topology—a terrific way to get an overview of a group of servers. As a bonus, the ecora Web site offers a free service that can document your network remotely.