Basic Mail Transfer Protocol (SMTP), answering our ubiquitous get in touch with to e mail, makes use of a spooled, or queued, technique of mail delivery. As soon as a message has been sent to a destination, the message is spooled to a deviceusually a disk. The server software in the destination posts a vigil, routinely checking the queue for messages. When it detects them, it proceeds to deliver them to their destination. SMTP is applied to send mail; POP3 is applied to obtain mail.