Exchange Protocols Documentation is live on MSDN
Today Microsoft released preliminary protocol documentation for Exchange 2007 (as well as Microsoft Office 2007 and SharePoint Server) as part of Microsoft's Interoperability Principles. The Exchange protocolsare now publicly available on the Open Protocol Specifications section of MSDN in preliminary form for developers to review and provide feedback. You can read more about the announcement in this press release.
Read more at source: http://msexchangeteam.com/archive/2008/04/08/448650.aspx