Hi,
1. If you're not using the last Hikashop version (2.2.0) you should probably download the last Hikashop version and install it again.
2. If you are receiving this kind of mail it probably means that the payment process went wrong.
3. If you really don't want to receive this mail you'll just have to edit the 'plugins\hikashopshipping\usps\usps.php' file and change these lines :
$email->subject = JText::sprintf('NOTIFICATION_REFUSED_FOR_THE_ORDER','Alipay').'invalid response';
$email->body = JText::sprintf("Hello,\r\n An Alipay notification was refused because the response from the Alipay server was invalid")."\r\n\r\n".$order_text;
$this->modifyOrder($order_id,null,false,$email);
by
$email->subject = JText::sprintf('NOTIFICATION_REFUSED_FOR_THE_ORDER','Alipay').'invalid response';
$email->body = JText::sprintf("Hello,\r\n An Alipay notification was refused because the response from the Alipay server was invalid")."\r\n\r\n".$order_text;
$this->modifyOrder($order_id,null,false,'');