On local machines and the heroku dev instance, we are using mailgun for emails.

For staging & prod we will need to use SES. To use SES, we will need to:

1. Change the SMTP config to SES (See bug 1480435)
2. Specify a configuration set with an SMTP header: X-SES-CONFIGURATION-SET: <ConfigSet> (See docs)
3. Add a /ses/notification endpoint to handle email bounce notifications and delete those users from our subscribers
4. Add authentication (HTTP basic auth or digital signature verification) to /ses/notification