Adds mailer layout to instructions emails

config/initializers/devise.rb

@@ -266,3 +266,7 @@ Devise.setup do |config|
   # so you need to do it manually. For the users scope, it would be:
   # config.omniauth_path_prefix = '/my_engine/users/auth'
 end
+
+Rails.application.config.to_prepare do
+  Devise::Mailer.layout "mailer" # email.haml or email.erb
+end