(Refers to systems that use paper to write), namely the postal system, the agency responsible for receiving mail is the postal company's model. (In the case of Thailand is If it is on the Internet, the thing that is responsible for sending mail is that all computers that act as e-mail servers. So if you want to use E- mail. The first thing you need to do is to subscribe or to register with an email server. Can be any server The mail server may be classified into three types.