Also, if I am not wrong, we will be sending emails *only* if the user introduces its contacts details (which is not the most common case). Can we also use the registered email in case that the user doesn't enter its contacts details in the feedback form? Note https://github.com/mariopl/firefoxos-dogfood/blob/5215a8cc027cf584de66c6c7588883b2c3b0a6d4/routes/feedback.js#L63

We store an email for each registered user associated with a registered device IMEI. Let's use that info if the user doesn't provide a new one.