@javier-matute-barragán the short answer is: please open an feature request to the Moquette project https://github.com/moquette-io/moquette/.

Long answer: Moquette could grab the remote IP from the incoming connection, but that wouldn't necessarily be the originating host, maybe because in the middle there is a proxy or similar. I would suggest that each client discover his external IP, and using user-properties communicate down the broker (only in MQTT 5) and that point the InterceptConnectMessage would contains also such user properties, and for this you also need to create a feature request.