Internet Information Server 4.0 provides both SMTP and NNTP servers. The SMTP server component provides a new method for a web application built using Active Server Pages on IIS 4.0 to dynamically send Internet mail, while the NNTP server allows for the hosting of newsgroups.
We will be looking at the SMTP service and – more particularly – at the interface that is provided through the Collaboration Data Objects for Windows NT Server (there is no corresponding interface for the NNTP service). That should help us to determine just what we can and cannot do with it. However, it is worth pointing out from the outset that one of the things that IIS 4.0 does not give you is a POP3 server. What this means is that although you will be able to use IIS 4.0 to send Internet Mail, you might struggle to use it as a full mail server. The lack of POP3 functionality means that although there is a mechanism for storing incoming messages, there is no method for the automatic delivery of incoming mail messages to the desktop of individual users.
In fact, the SMTP service does provide a universal inbox into which all incoming messages are placed. Later on in this chapter we will look at how you can read the inbound messages addressed to specific users from an Active Server Page. However, for more comprehensive functionality, many users will feel tempted to implement a product such as Microsoft Exchange Server, which provides both SMTP and POP3 support. In essence, the SMTP server component of IIS 4.0 has been designed to make the process of creating and sending Internet Mail messages as easy as possible. It's quick and it's easy, it may well be all you need for mail-enabling your web site, but it probably won't be the answer to all your messaging problems.