Just a quick note. MS is continuing to follow-through on the interop principles commitment made earlier this year. MS announced that >14,000 pages of preliminary documentation of client/server protocols has been posted to the web.

The documentation is for:

• Protocols between Microsoft Office SharePoint Server 2007 and Office client applications
• Protocols between Microsoft Office SharePoint Server 2007 and other Microsoft server products
• Protocols between Microsoft Exchange Server 2007 and Microsoft Office Outlook
• Protocols between Microsoft Office 2007 client applications and other Microsoft server products

This brings the total amount of protocol documentation to more than 44,000 pages posted to the web based on the interop principles. The point of the "preliminary" status of the posted documentation is that the community has an opportunity to provide feedback on the documentation.

In the end, these docs make it possible for software engineers doing work for ISVs, in the OSS community, in IT departments, in government agencies, or wherever to have consistent, open access to the information that shows how these Microsoft products communicate with each other. 

This table may be helpful for you if you are interested in learning more about the documentation.