There are several standards that are widely supported as ways of transferring mail around a local area network. There is Microsoft's own standard, called MAPI (mail-API), which is supported by almost all of its applications. It is a good choice for Visual Basic mail applications because VB includes a component that does much of the hard work! Alternatives to MAPI include VIM (a rival standard supported by Lotus and other vendors) and MHS (an independent standard often used as a post office or gateway between different mail systems).

Using VB to create a simple electronic mail program means that you can create a product that is as simple or complex as you require. If you are developing for end users who have never used email, you can design the simplest mail program in just a few steps. To start with, you need not worry yourself or the user with attachments, type of delivery or receipts. Once the users have got into the swing of email, simply extend your mail program to add in the other functions all are supported by the MAPI component and accessed by its properties or functions. A typical example would be to create a simple Windows mail application to access a text-only mainframe mail utility once you have configured MAPI to deal with the mainframe's mail protocol, the front end is very simple to create.

Figure 5.1: Microsoft Exchange uses MAPI calls to transfer email.

One of the most...