MAPI is a powerful and flexible method for gaining access to messaging capability. Unfortunately, MAPI is not directly accessible to Visual Basic applications. Several messaging technologies are accessible to Visual Basic, some of them providing an interface to MAPI and others ignoring MAPI altogether. The following sections briefly describe these technologies and the circumstances under which they should (or shouldn’t) be used.
You can think of both Microsoft Outlook and Microsoft Exchange as feature-rich wrappers over the MAPI subsystem. When developing Microsoft Outlook and Exchange, Microsoft decided to use some of the MAPI features and abandoned others. As a result, you do not get some events or event details when the user deletes the last item in a Microsoft Outlook folder, changes the item in an Microsoft Outlook Explorer window, deletes more than 16 items at once, and so on, and so forth.
