It would be really useful if I could simulate certain delivery outcomes in mailgun by using some special/reserved email addresses you've implemented.

For example, I'd like to be able to specify something like "bounce@test.mailgun.com" as a recipient, and have mailgun instantly treat the message as a bounce and notify my webhook.

Some of your competitors provide this functionality to their customers, e.g. http://docs.aws.amazon.com/ses/latest/DeveloperGuide/mailbox-simulator.html