wrap_delivery_behavior

# File actionmailer/lib/action_mailer/delivery_methods.rb, line 58
      def wrap_delivery_behavior(mail, method = nil, options = nil) # :nodoc:
        method ||= delivery_method
        mail.delivery_handler = self

        case method
        when NilClass
          raise "Delivery method cannot be nil"
        when Symbol
          if klass = delivery_methods[method]
            mail.delivery_method(klass, (send(:"#{method}_settings") || {}).merge(options || {}))
          else
            raise "Invalid delivery method #{method.inspect}"
          end
        else
          mail.delivery_method(method)
        end

        mail.perform_deliveries    = perform_deliveries
        mail.raise_delivery_errors = raise_delivery_errors
      end