This has a real "Windows NT is secure if you don't connect it to a network" vibe. If you don't want others to ever know your IP address, don't connect to the Internet. If you actually care about people not learning your IP address and still want to connect to the Internet, take some time to learn how email has worked for the last forty years. Don't get on the Internet, then act shocked that things that're decades old aren't how you want or expect them to be.