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Network Working Group J. Postel
Request for Comments: DRAFT ISI
Replaces: RFC 788, 780, 772 August 1982
SIMPLE MAIL TRANSFER PROTOCOL
1. INTRODUCTION
The objective of Simple Mail Transfer Protocol (SMTP) is to transfer
mail reliably and efficiently.
SMTP is independent of the particular transmission subsystem and
requires only a reliable ordered data stream channel. Appendices A,
B, C, and D describe the use of SMTP with various transport services.
A Glossaryprovides the definitions of terms as used in this
document.
An important feature of SMTP is its capability to relay mail across
transport service environments. A transport service provides an
interprocess communication environment (IPCE). An IPCE may cover one
network, several networks, or a subset of a network. It is important
to realize that transport systems (or IPCEs) are not one-to-one with
networks. A process can communicate directly with another process
through any mutually known IPCE. Mail is an application or use of
interprocess communication. Mail can be communicated between
processes in different IPCEs by relaying through a process connected
to two (or more) IPCEs. More specifically, mail can be relayed
between hosts on different transport systems by a host on both
transport systems.
Postel [Page 1]