$ rake 'emails:test[michael@example.com]'
Testing sending to michael@example.com using mx-out:25.
SMTP server connection successful.
Sending to michael@example.com. . .
Mail accepted by SMTP server.
If you do not receive the message, check your SPAM folder
or test again using a service like http://www.mail-tester.com/.
If the message is not delivered it is not a problem with Discourse.
Check the SMTP server logs to see why it failed to deliver the message.