MAPI--the Messaging API--of course, isn't an API. It uses COM. It also isn't directly accessible from Visual Basic, which is why you need CDO. MAPI is a game of two halves. The original MAPI is accessible via VB API calls. It was replaced with Extended MAPI and renamed to Simple MAPI. In CDO and MAPI Programming with Visual Basic
the author covers Simple MAPI, used for client apps, for backward compatibility. As he points out, it's useful when all you want to do is send an e-mail from an application and don't need the complexity of Extended MAPI.
The good stuff starts in chapter five where it is explained how VB's access to COM is, bizarrely, inferior to CDO's COM access. In practice, a useful aspect of this book is finding out which bits of Microsoft's messaging technology go where, what can get at them and how to locate and install the various files essential to making it all work.
As you would expect, you get to build a fully featured mail client which exercises most of MAPI. There is also an introduction to using the CDO Rendering Library on servers with IIS and ASP. The server side gets more coverage with a discussion of CDO for Windows 2000, aimed at creating server side apps. Unlike CDO 1.21 it doesn't use MAPI.
Even Simple MAPI is so complex, often requiring what look like duplicate calls to work, that Microsoft created helper applications for it; but the author successfully sends the message that CDO makes using MAPI more straightforward than you might think. --Steve Patient
Computers and devices are more connected now than ever before. Why? Because the humans who use those computers need to collaborate. We need to share information, and we need to do it quickly, without regard to the physical distance that separates us. Corporate solution developers now more than ever have the opportunity and responsibility to enable people to communicate in ways never before possible. CDO and MAPI Programming with Visual Basic: Developing Mail and Messaging Applications dives deep into Microsoft's Collaboration Data Objects (CDO) and the Messaging Application Programming Interface (MAPI), then moves into succinct explanations of the types of useful messaging applications that can be written in Visual Basic. Microsoft has given the Visual Basic community Collaboration Data Objects (CDO)--a technology that goes far beyond simple email, fully into the realm of information workflow. CDO enables Visual Basic applications to exchange not only classic email, but in fact any information in a straightforward and easy way. The Internet--sometimes seen as a barrier by developers--is turned into an open pipe, ready to take your application's data around the world.
Routing documents and building email list servers is just the beginning. Harness the power of worldwide communication in your everyday business applications. MAPI is the cornerstone of messaging on the Windows platforms, and profoundly influences the way you will write your collaboration applications. Understanding this technology lays the foundation for adding effective collaboration capabilities to your own applications. CDO and MAPI Programming with Visual Basic: Developing Mail and Messaging Applications fills a gap in an exciting and relatively young, yet popular, technology that lacks adequate documentation.