Mail gateway

Mail gateway, a computer, it will email transmitted from one network to another network, from a network to the Internet or on the contrary, when necessary to rearrange the header ( header ) message format.
The gateway was very easy to understand the concept of. In the early days of the Internet, term gateway refers to the router. A network router is beyond the local network marking, this to the unknown" gate" once, is still used in the calculation of routing and packet data is forwarded to a source outside of the network, therefore, it is considered to the Internet gateway. With the passage of time, the router no longer magical, public IP based wide area network router and maturity to promote growth. Now the routing function can also be composed of a host machine and a switching hub to exercise, the gateway is no longer mysterious concept. Now, the router becomes a multifunctional network equipment, it can be divided into several segments, LAN interconnection of private wide area network LAN and related to the wide area network interconnection and the formation of the Internet, so that the router will lose their original concept of gateway. However the term gateway still followed down, has been applied to a variety of different functions, defining gateway is no longer easy.