A standard protocol used for transmitting email over the Internet. This protocol is the way most Internet mail clients talk to most Internet mail servers. It is also the way most Internet mail servers communicate with other Internet mail servers.

SMTP is the facility which allows you to send email to the intended recipients.

A TCP/IP protocol for sending messages from one computer to another on a network. This protocol is used on the Internet to route e-mail.

Simple Mail Transport Protocol, a protocol used by mail servers and clients to transfer emails across the network.

often referred to as send mail, is designed to allow the delivery of mail messages to Internet users