Just an answer from the dev team here to get the ball rolling... You'll need to have a 3rd party mail server. There are two options:
- A traditional email server running POP3 or IMAP. This is a "pull" protocol, so you'll need to write a scheduled task to poll it and pull down any waiting emails periodically.
- A web service that does webhooks to notify you of incoming emails. I remember hearing from someone who was using something like this, but unfortunately can't find the details. Basically, you set it up to receive emails for your domain, and then when one arrived, it hit a URL that you defined. So you could set up a URL on your web app so that when it was pinged by the service, it did appropriate stuff.
Anyway, that's what's possible in theory, as far as I know. Hopefully other people can chime in and say how they're doing it in practice :-)