Understanding the Workgroup Extensions

The workgroup extensions for Word provide functions that mirror MAPI functions. Since WordBasic cannot directly manipulate MAPI data types such as messages or recipient lists, the MAPI data types are managed by the WBMAPI.DLL library. The library, in turn, provides WordBasic handles to the MAPI data types. All references to MAPI data types are made by referencing handles. The WBMAPI.DLL library provides functions to create and destroy MAPI data types, as well as to examine and manipulate fields within MAPI
data types.

When a WBMAPI.DLL function is successful, it returns a handle as a non-negative value. When a function is not successful, it returns a MAPI error value
as a negative integer.