This isn't really a mock, or it's kind of like a mock combined with a utility class. I would be tempted to create a mock email which is just that, and which has the properties that an email should have, and then also create an email utility class (similar to what @rwood-moz did with the bluetooth utils in pull request #704).

There is a bit of a precedent set for a self-populating mock which "does things" with the `PersonaTestUser` class [1], but if you want to follow that model then I think this should be called an EmailMessage (for example) as opposed to a MockEmail, and it should probably send the email via the `__init__` method rather than via a separate method which has to be called on the object.


[1] https://github.com/mozilla/gaia-ui-tests/blob/master/gaiatest/mocks/persona_test_user.py