gistfile1.txt

class BadUsernameMailer < ActionMailer::Base
  layout 'mailer'
  default from: "[email protected]"

  def username_changed_email(user,old,new)
    @old = old
    @new = new
    mail(:to => user.email, :subject => "uFlavor - Important Account Information - username changed")
  end
end

From the rails guides...

class UserMailer < ActionMailer::Base
def welcome_email(user)
mail(:to => user.email) do |format|
format.html { render :layout => 'my_layout' }
format.text
end
end
end