protected function _normalize($obs)
    {
        $add = array();

        if (!($obs instanceof Horde_Mail_Rfc822_List) &&
            !is_array($obs)) {
            $obs = array($obs);
        }

        foreach ($obs as $val) {
            if (is_string($val)) {
                $rfc822 = new Horde_Mail_Rfc822();
                $val = $rfc822->parseAddressList($val);
            }

            if ($val instanceof Horde_Mail_Rfc822_List) {
                $val->setIteratorFilter(self::BASE_ELEMENTS);
                foreach ($val as $val2) {
                    $add[] = $val2;
                }
            } elseif ($val instanceof Horde_Mail_Rfc822_Object) {
                $add[] = $val;
            }
        }

        return $add;
    }