    # File lib/rfilter/delivery_agent.rb, line 342
          def exitcode(exception)
            case exception
            when DeliverySuccess
              RFilter::MTA::EXITCODE_DELIVERED
            when DeliveryReject
              RFilter::MTA::EXITCODE_REJECT
            when DeliveryComplete
              RFilter::MTA::EXITCODE_DEFER
            else
              raise ArgumentError,
                "argument is not a DeliveryComplete exception: " +
                "#{exception.inspect} (#{exception.class})"
            end
          end