A vulnerability scan of Messaging Gateway (SMG) indicates that Messaging Gateway is configured as an open SMTP relay.
A mail server is explicitly configured to allow SMTP mail relay, which allows abuse by spammers.
The Outbound SMTP interface on Messaging Gateway is configured as a trusted relay for the internal customer network. This is by design and access to the Outbound MTA is limited by an access control list (ACL).
This entry in a vulnerability scan is a false positive. The Outbound MTA on Messaging Gateway is configured as a trusted relay for all networks configured in the Outbound Mail Acceptance list.
To update the Outbound Mail Acceptance list