Basically, my end goal is to have an email server which can randomly generate email addresses. People can then send attachments to these addresses, and if sent the correct email, it will attach the file to their account on my application.
What I'm looking for is very similar to Posterous' email system, which generates one email address for you to email your blog posts to.
It's also similar to Facebook's comment-email system, where it sends you an email every time you get a notifications (you got tagged, someone commented on something you posted, etc), and all replies sent to that email are recorded as comments to the specific notification.
How is this done?