Professor Aars,
We are using the Devise mailer, which uses actionmailer's configuration. The format for the mail that is sent is stored in the app/views/devise/mailer directory, and configuration of the mailer is stored in each of the environment files located in config/environments as well as config/initializers/devise.rb.
Devise hides most of the actual use, as we are mainly using default configurations, it just kind of handles the work itself through the devise models/controllers that are located in the gem, and not our app directory.
I hope that answered your question, if not I can try again
-Logan