If you are developer working on MAPI then here is the news:
MAPI documentation is revamped and republished on MSDN
Welcome to the Outlook 2007 MAPI Reference
Angela also talked about it @ http://blogs.msdn.com/officedevdocs/archive/2009/01/20/where-is-the-mapi-documentation.aspx
For what is new and what has changed visit:
What's New in This Edition
And if you are looking for sample code related to MAPI then there is no better sample available than MFCMAPI.
MFCMAPI as a Code Sample
Also don't get confused with "MAPI Canonical Properties" http://msdn.microsoft.com/en-us/library/cc979184.aspx
Because canonical properties are not real properties and are not defined in MAPI header files, you should NOT use canonical property names in code; instead, you should continue to use the exact MAPI property names in code.
Now, there are now close to 900 properties documented, including tagged properties and named properties. So let's explore...