Outlook Blocked harmful attachment

The attachment that was sent to me was from a friend I knew what was in the attachment and it was something I needed right away nothing in it that would harm my computer in any way the message on the e-mail said Outlook Blocked the attachment they thought it was harmful I phoned outlook and the customer service guy said they Do Not Block Mail with Attachments he said it had to be my Norton Security program if that is true why does Outlook put on it that they Blocked it ????