protected function _package_master_elements($envelope, $targeting, $scheduling) {
        $ret = false;

        if ($envelope instanceof \Yesmail\YesmailMasterEnvelope && $envelope->is_valid() === true) {
            $ret = new \stdClass();
            $ret->envelope = $envelope;

            if ($targeting instanceof \Yesmail\YesmailMasterTargeting && $targeting->is_valid() === true) {
                $ret->targeting = $targeting;
            }

            if ($scheduling instanceof \Yesmail\YesmailMasterScheduling && $scheduling->is_valid() === true) {
                $ret->scheduling = $scheduling;
            }
        }

        return $ret;
    }