Mail Transfer Protocol
RFC 772
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RFC - Unknown
(September 1980; No errata)
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2013-03-02
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RFC 772 (Unknown)
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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 response to a
MTP command. The general form of a reply is a completion code
(including error codes) followed by a text string. The codes
are for use by programs and the text is usually intended for
human users.
receiver-MTP process
A process which transfers mail in cooperation with a sender-MTP
process. It "listens" on its port/socket L for a connection
from a sender-MTP and establishes a control connection using
the TELNET Protocol. It receives MTP commands from the
sender-MTP, sends replies, and governs the transfer of mail.
sender-MTP process
A process which transfers mail in cooperation with a
receiver-MTP process. A local language may be used in the user
interface command/reply dialogue. The sender-MTP initiates the
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