public function sort(array $opts = array())
    {
        $this->_delimiter = isset($opts['delimiter'])
            ? $opts['delimiter']
            : '.';
        $this->_sortinbox = (!isset($opts['inbox']) || !empty($opts['inbox']));

        if (empty($opts['noupdate'])) {
            $mboxes = &$this->_mboxes;
        } else {
            $mboxes = $this->_mboxes;
        }

        uasort($mboxes, array($this, '_mboxCompare'));

        return $mboxes;
    }