SMTP

SMTP, the Simple Mail Transfer Protocol, is the Internet standard protocol mail servers and other message transfer agents use to send and receive electronic mail, first specified in RFC 788 in November 1981 with major input from Jon Postel. It defines how one mail server hands a message to another across a network, and it remains the protocol that carries mail between servers today even though separate protocols such as POP3 and IMAP handle a mailbox's retrieval by an end-user client. SMTP has been revised several times, most significantly in RFC 5321, while keeping its original command-and-response design. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/