public function folder_classname($folder_id)
    {
        if ($folder_id == 'INBOX') {
            return 'inbox';
        }

        // for these mailboxes we have localized labels and css classes
        foreach (array('sent', 'drafts', 'trash', 'junk') as $smbx)
        {
            if ($folder_id === $this->config->get($smbx.'_mbox')) {
                return $smbx;
            }
        }
    }