title: Mail sent to a .herokuapp.com domain
body: <p>I would like to configure Heroku and Mailgun to send email from and allow me to receive webhooks (which are POSTs Mailgun sends notifying me of email sending statuses) at a [myapp.]herokuapp.com domain while buying as few additional things as possible. I don't want to buy another domain name, but it doesn't appear that I can avoid that. I'd like to avoid buying another SSL endpoint; it doesn't appear to be necessary and I don't need privacy. What do I need to buy?</p>