Exchange 2016 setup openrelay ip
550 5.7.54 SMTP; Unable to relay recipient in non-accepted domain
Under mail flowAdd a new FrontendTransport call it openrelaySet security to TLS and check the box for Anonymous UsersScopping set the ips above that you want to allow and then port 25Get-ReceiveConnectorGet-ReceiveConnector SERVERNAME\openrelayGet-ReceiveConnector (SERVERNAME)\openrelay | Add-ADPermission –User “NT Authority\Anonymous Logon” –ExtendedRights “ms-Exch-SMTP-Accept-Any-Recipient”
Try it out