The Messaging Application Programming Interface (MAPI 1.0) is a set of object-oriented functions that provide messaging capabilities. Mail-enabled applications use MAPI to create, transfer, and store messages, as well as handle complex addressing information. MAPI objects are data structures that support a set of properties and comply with the OLE component object model (COM), which requires that objects support one or more interfaces, or sets of functions.
See the GroupWise MAPI SDK.