Microsoft is publishing many of their “closed” protocols on the internet.
The starting site is: Microsoft Protocol Programs and Open Specifications.

Here is just a small list of available protocol downloads:

• Office File Formats Documentation (containing ppt, doc, xls, …)
• Windows Communication Protocols (MCPP)
• Windows Server Protocols (WSPP)
• Application Services and .NET Framework Protocols
• Microsoft Office Protocols
• SharePoint Products and Technologies Protocols
• Exchange Server Protocols
• Microsoft SQL Server Protocols
• Microsoft Exchange Server Standards
• Microsoft Office Standards Documents