There are numerous ways to send emails using ASP. The simplest way, in my opinion, is to use CDO, the free emailing component which comes packaged with NT Option Pack 4. There is already an article on the site which delves into a rigorous discussion of how to use CDO. This article pertains to non-CDO approaches. If you're interested in using/learning about CDO, why not read the article?
Why not use CDO?
CDO is not designed just for emailing. If you've ever used Outlook, you know that Outlook is not designed just for email either. There are appointments, calendars, journal entries, reminders, etc. CDO is like that too. You can use CDO to send people reminders and accomplish other neat MS Office related tasks. Of course, added functionality equates to increased size and a decrease in efficiency. Therefore, many people will tell you that CDO is bloated and slow. While it is not as fast as the ASP components discussed below, it is not a terrible mailer. Unless you plan on sending out hundreds of emails a day, I doubt you will notice a speed difference between CDO and any of the components below.
So, does it matter what component you choose? Not really, not unless you plan on doing some heavy duty emailing. Some of the components discussed below are free (as is CDO), they all have relatively the same features when it comes to emailing, and they are all pretty easy to use. Personally, I like CDO, so I haven't bothered learning another component. If you can't decide which is best for you, hell, just pick one at random. :)
Cost: FREE! :)
From Persist Software, the folks who do ASPUpload Cost: Free (Can purchase the source code for $185.00)
A heavy duty emailer!
For more information on ASPQMail, and other related email/ASP components, be sure to visit ServerObjects.com.