protected function clear_mailbox_cache()
    {
        $this->clear_status_cache($this->selected);

        $keys = array('UIDNEXT', 'UIDVALIDITY', 'HIGHESTMODSEQ', 'NOMODSEQ',
            'PERMANENTFLAGS', 'QRESYNC', 'VANISHED', 'READ-WRITE');

        foreach ($keys as $key) {
            unset($this->data[$key]);
        }
    }