Mail Transfer Protocol (RFC0772)

Network Working Group S. Sluizer Request for Comments: 772 J. Postel ISI September 1980

MAIL TRANSFER PROTOCOL

PREFACE

This is a first draft of this protocol and comments are very definitely requested.

INTRODUCTION

The objective of Mail Transfer Protocol (MTP) is to transfer mail reliably and efficiently.

This paper assumes knowledge of the following protocols described in the ARPA Internet Protocol Handbook. The reader will note strong similarities to portions of the File Transfer Protocol; in part, this is due to the original ARPA Network implementation of computer mail as a feature of FTP.

The ARPANET Host-to-Host Protocol [Network Control Protocol] (NCP)

The Transmission Control Protocol (TCP)

The TELNET Protocol (TELNET)

The File Transfer Protocol (FTP)

DISCUSSION

In this section, the terminology and the MTP model are discussed. The terms defined in this section are only those that have special significance in MTP. Some of the terminology is very specific to the MTP model; some readers may wish to turn to the section on the MTP model while reviewing the terminology.

TERMINOLOGY

ASCII

The ASCII character set as defined in the ARPA Internet Protocol Handbook. In MTP, ASCII characters are defined to be the lower half of an eight-bit code set (i.e., the most significant bit is zero) and is called NVT-ASCII.

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September 1980 RFC 772 Mail Transfer Protocol

control connection

The TCP full-duplex communication path or two NCP simplex communication paths between a sender-MTP and a receiver-MTP for the exchange of commands, replies, and mail text. The control connection operates according to the TELNET Protocol.

data mode

The mail is transmitted over the control connection as a stream of octets. (In FTP terminology this is called stream mode.)

data structure

The internal structure of mail is considered to be a continuous sequence of data octets. (In FTP terminology this is called file-structure.)

data representation

The internal representation of all data (i.e., mail) is in NVT-ASCII.

host

A computer in the internetwork environment on which mailboxes reside.

MTP commands

A set of commands which comprise the control information flowing from the sender-MTP to the receiver-MTP.

mail

An ordered set of computer data of arbitrary length, which conforms to the standard set in RFC 733 (Standard for the Format of ARPA Network Text Messages).

mailbox

A character string (address) which identifies a user to whom mail is to be sent. Mailbox normally consists of the host and user specifications. The standard mailbox naming convention is defined to be "user@host". Additionally, the "container" in which mail is stored.

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RFC 772 September 1980 Mail Transfer Protocol

NVT

The Network Virtual Terminal as defined in the TELNET Protocol.

octet

Bytes in MTP are octets (8 bits). This is not necessarily the same byte size in which data is stored in a host.

reply

A reply is an acknowledgment (positive or negative) sent from receiver to sender via the control connection in...