Exactly. We can't just sit down and write you a tutorial based on the fact
that you don't know where to get started. If you want quick responses, you
have to show what you've already tried and why it doesn't work, and ask
a specific question.
What part of that is confusing you? The "automatically" part? What do you mean by "automatically"?
Normally you'll need a server program running and polling the INBOX for the return receipt address
for new messages.