$ date Wed Nov 25 18:48:08 CET 2020 $ nc -z -v -w3 104.47.5.36 25 nc: connect to 104.47.5.36 port 25 (tcp) failed: Connection refused $ nc -z -v -w3 104.47.6.36 25 nc: connect to 104.47.6.36 port 25 (tcp) failed: Connection refused tcp/587 dettó.