I have a web app that create groups. Each group gets their own discussion board.

I would like to add the feature of allowing users to send emails to their "group" within the web app to start a new discussion or reply to an email from the "group" to make a new post in an already ongoing discussion.

For example, to start a new discussion a user would send:
From: [email protected]
To: [email protected]
Subject: Hey guys! Meet up on Tuesday?
Body: Yes? No?

All members of the group would receive an email:
From: [email protected]
Subject: Hey guys! Meet up on Tuesday?
Body: Yes? No?
Reply-To: group1@ example.com

And, the app would start a new discussion with:
Author: Bill Fake
Subject: Hey guys! Meet up on Tuesday?
Body: Yes? No?

This is a pretty standard feature for Google Groups and other big sites. So how do us mere mortals go about implementing this? Is there an easy way?

Or do I:
1. Install postfix
2. Write scripts to create new accounts for each new group
3. Access the server periodically via pop3 (or imap?) to retrieve the email messages sent to each account?
4. Parse the message for content

If it's the latter, did I miss a step?