The bloody McAfee caused another trouble yesterday by rereleasing the new DAT 6682. Our Exchange server transport server stopped working just after updating to the DAT6682. The only thing you can do is to revert the DAT back to 6681 in both ePO master repository and the mail server.

The solution can be found at: https://kc.mcafee.com/corporate/index?page=content&id=KB70380