An SMTP listener can be configured to send and receive e-mail. In a typical Microsoft Environment, Exchange Server is usually used to accomplish this, though, and it is rarely located on the same server that serves as "the Web server."
To verify that your SMTP listener is working, you can send it some mail using telnet to port 25. telnet localhost 25 should do the trick.
The conversation protocol goes typically as follows:
EHLO (or HELO)
MAIL FROM: (valid e-mail address)
RCPT TO: (valid e-mail address)
DATA
From: (e-mail)
To: (e-mail)
Subj: (subject)
Body of e-mail
. (type a period)
(press enter a couple times)
Quit
That will queue a message for delivery using SMTP. If you want to use Outlook or Outlook Express to connect to your server, you probably want to configure POP3.
However, with a simple SMTP listener and some readily-available ASP code, you can have a basic e-mail service up and running very quickly, cheaply and easily. Read up on "open relay" before attempting this.
Here's some detailed info:
Len