Mailer should give self as payload because it contains all the information...

Mailer should give self as payload because it contains all the information needed (as the template rendered and the mailer name).

actionmailer/lib/action_mailer/base.rb

@@ -499,7 +499,7 @@ def deliver!(mail = @mail)
         logger.debug "\n#{mail.encoded}"
       end
 
-      ActiveSupport::Notifications.instrument("action_mailer.deliver", :mail => mail) do
+      ActiveSupport::Notifications.instrument("action_mailer.deliver", :mail => self) do
         begin
           self.delivery_method.perform_delivery(mail) if perform_deliveries
         rescue Exception => e # Net::SMTP errors or sendmail pipe errors