Mail delivery problem to server error 530 5.7.1 client was not authenticated

This is the message the sender of the mail receives:
Client not authenticated, why? not activated yet.

The error 530 5.7.1 client was not authenticated is issued by the exchange server when the client trying to connect is not authenticated. So it seems that the exchange server is not configured to accept connections from the Protector. Here follows the test conducted on mail.example domai that demonstrates it. The ip 192.168.100.5 is the IP address of the mail server.

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To fix it, it should be enough to follow these steps:
    Login to Exchange server.
    Go under your Exchange Organization-->Server configuration-->
    Click on Hub transport and Select the server default receive connector.
    Right click and select properties
    Click on last tab “permission Groups”
    Place check mark into “Anonymous users”
    Click Apply and OK