In Word, MAPI is hosted by the WordBasic language. In some ways, WordBasic is the most limited of all the versions of Basic. Limitations on passing strings and a lack of user-defined types necessitates the use of a "wrapper" DLL, WBMAPI.DLL, to implement mail functionality within Word. This DLL changes the MAPI interface to a form that WordBasic can understand. WBMAPI.DLL, in turn, communicates with MAPI.DLL.
WBMAPI.DLL adds several new functions to deal with attachments and recipients since WordBasic cannot manipulate user-defined types directly.
From the Word developer's point of view, a series of functions from WBMAPI.DLL are declared in the body of a WordBasic macro. Both WPMAPI.DLL and MAPI.DLL must be present to use these functions.
The full set of declarations and support routines are provided and described in the Word sample application described later in the paper.