What is the "Simple MAPI" ?

Simple MAPI is a subset of 12 functions, which enable developers to add basic messaging functionality to their Windows-based applications.

It includes functions to support sending and receiving messages:

Log onto the messaging system.
Compose new messages, add and resolve recipients, send messages.
Retrieve and read messages from the inbox.

The Simple MAPI functions can be called from any application that supports both making API calls as well as the structures and data-types used by Simple MAPI, such as C, C++, Visual Basic, and Visual Basic for Applications (VBA).

"The MAPI controls included with Microsoft Visual Basic (versions 3 through 6), and the version of MAPI installed by Outlook Express implement Simple MAPI only."