As an app developer, one of the things that I hate having to set up is a reliable way to email users. Setting up your own email server can be a giant pain and the odds are decent your email will end up in a spam folder anyway. Fortunately, Mailgun abstracts all the complexity behind sending a message behind an easy to use API.
In the screencast below, I give a quick walkthrough on how to setup Mailgun. The bonus of being a Rackspace customer is that you are able to process 50,000 free messages each month. For more documentation on how to use Mailgun, you can visit http://documentation.mailgun.com.