554 5.2.3 Mail Policy violation Error delivering to mailboxes

554 5.2.3 Mail Policy violation Error delivering to mailboxes

Hi team,

For the past couple of days i am facing a serious issue with my Zoho mail box.
When someone tries to send mail on our ID's with some attachments it returns an error message like the below. 

But the interesting thing is some other mail's are delivering normally.Don't know what really happened.

" 554 5.2.3 Mail Policy violation Error delivering to mailboxes "

Domain : hexecon.com
User ID : 644951266


Please get this sorted out at the earliest.


Thanks & regards,