Access Control:  Denied by customer-specified access lists (MAPS & Global IP Deny) and domain & user Deny Lists.  These messages contain specific information about the reason for the bounce such as “Mailhost / Sender is on the Domain Deny List” or “Mailhost / Sender is on the Global Deny List” or “Recipient does not accept mail from XXXX”.

Our users may specify senders, IP addresses and domains from which they do not wish to receive email. 

If you believe that the message is legitimate and should be delivered, contact the recipient and let them know what you are seeing and request that they Whitelist / Allow your sending address.