public function set($mailbox, $data, $uidvalid)
    {
        $mailbox = strval($mailbox);

        if (empty($data)) {
            $this->_backend->getMetaData($mailbox, $uidvalid, array('uidvalid'));
        } else {
            $this->_backend->set($mailbox, $data, $uidvalid);

            if ($this->_debug) {
                $this->_debug->info(sprintf(
                    'CACHE: Stored messages [%s; %s]',
                    $mailbox,
                    $this->_baseob->getIdsOb(array_keys($data))->tostring_sort
                ));
            }
        }
    }