552 5.2.0 Prohibited by policy

HI,

Need a support on Email got blocked by comcast ISP. Yesterday evening we have sent an email with attachment of 10MB in size. And we got a block error.

" The comcast.net server blocked this message from being delivered. While we won't try to send this message again, we will attempt to send new messages to this address in the future."
                      
                  
The error that the other server returned was: 552 5.2.0 Prohibited by policy

What is happened suddenly Please advise on the same.

Thanks & Regards

<Edited: "Personal Information">