VIM and MAPI

Our discussion has concentrated on various Internet-based standards that involve sending e-mail. However, this isn't the complete story, much as we'd like to concentrate on 100% pure Internet e-mail. There are two other standards that are worthy of mention, and they have nothing to do with the Internet whatsoever: the Vendor Independent Messaging (VIM) standard, and the Mail Applications Protocol Interface (MAPI).

Despite their names, both standards try to accomplish the same task: to define a mechanism for how desktop applications can invoke an e-mail program and send a message from within the application. This sounds simple, but there is a lot of difficulty with actually implementing this interface. First off, figuring out what basic operating system services are available to most applications isn't easy, especially if you want to architect the same services on Windows 3.1, 32-bit Windows, Unix and Macintoshes. Second, the notion of "sending a file" isn't implemented the same across applications.

Despite these difficulties, Microsoft and Lotus came up with their own interfaces. Both standards began their lives with different purposes.

VIM began with Lotus' cc:Mail as a single interface that would work across all the various operating system platforms and for all of the various cc:Mail products. Microsoft of course wasn't satisfied with the way VIM was put together and created its own MAPI for Microsoft Mail, the precursor to Exchange and Outlook. MAPI became part of the Windows operating system applications interface and is now supported by most Windows-based e-mail products, including cc:Mail, ironically. VIM is still being used by Lotus, although it seems to be in decline.

Both products install a series of dynamic linked libraries. This presents the challenge of keeping these files up-to-date, and ensuring that some application doesn't overwrite the latest version with some older version is always an interesting parlor game when it comes time to install some e-mail software. When an application, say, a word processor, wants to send a file via e-mail, it calls this library and sends the information to the e-mail program. When you install an e-mail program on your desktop, it registers itself as a MAPI or VIM service provider. For the MAPI programs, once they are registered, the application will appear on the Send To: menu when you right-click your mouse on a file shown either on your desktop or Windows Explorer. VIM programs require special programming to work within applications.

There is a great deal more complexity behind these two programming interfaces. In the next installment we'll examine some current products that implement the standards discussed here to provide solutions for sending Internet mail.