You received a Non-Delivery Report (NDR) for email sent through the Symantec Email Security.cloud infrastructure, with the message "You are trying to use me [server-X.tower-XXX.messagelabs.com] as a relay, but I have not been configured to let you [IP, address] do this."
453-you are trying to use me [server-X.tower-XXX.messagelabs 453-.com] as a relay, but I have not been configured to let 453-you [IP, server.address] do this. Please 453-visit https://knowledge.broadcom.com/external/article?articleId=169652 453-for more details about this error message and instructions to 453-resolve this issue
When the email is sent from a customer domain through the Symantec.cloud outbound to a 3rd party domain, check the following: