Question : Diagramming Exchange 2003 Message Flow

I would like to find out if there is a free utility for mapping and diagramming entire Exchange 2003 message flow in a very large organization. Also, can you please be as detailed as possible in describing the best ways to discover and analyze the mail flow system. I need the tools to collect all the mail flow data, then analyze it, and then make a Visio diagram.  It probably would be the best to find a tool that would allow me to export mail flow configurations into the spread sheet, and then into the Visio diagram.

Thank you very much

Answer : Diagramming Exchange 2003 Message Flow

http://www.microsoft.com/downloads/details.aspx?familyid=cb42fc06-50c7-47ed-a65c-862661742764&displaylang=en

Diagrams AD and Exchange into Visio.  Oh, and it is free.