What are the high level requirements for building a basic SMTP server for Windows?

Question

I know Windows has SMTP capabilities under IIS, but I thought a basic SMTP would be a good project for learning Windows application development. I don't want a relay. I want an actual SMTP server that will send email from localhost anonymously. Obviously, it is only to be used for routing emails sent during a development process, and I really wanted to know what I am up against.

1. Would VB.net be the most common approach?
2. Is it possible to route email anonymously (no username/password)?
3. What are some of the fine details I need to be thinking about?

Thanks!

Answer 1

You'll need to understand the SMTP protocol (or at least a reasonable subset of it). If you're familiar with C++, you could grab the source code for Blat to get an idea of how to create a simple mailing system.

Answer 2

You should read a book on networking protocols. If you want to do this from scratch, you need to keep an outgoing mail queue, you need to parse email addresses to find their hostnames, look up the DNS MX records of those domains, contact the server on port 25 and then talk SMTP.