public function removeMessage($id)
    {
        $filename = $this->_getFileData($id, 'filename');

        if ($this->_quota) {
            $size = filesize($filename);
        }

        if (!@unlink($filename)) {
            /**
             * @see Zend_Mail_Storage_Exception
             */
            // require_once 'Zend/Mail/Storage/Exception.php';
            throw new Zend_Mail_Storage_Exception('cannot remove message');
        }
        unset($this->_files[$id - 1]);
        // remove the gap
        $this->_files = array_values($this->_files);
        if ($this->_quota) {
            $this->_addQuotaEntry(0 - (int)$size, -1);
        }
    }