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Transition of Internet Mail from Just-Send-8 to 8bit-SMTP/MIME (RFC1428)

IP.com Disclosure Number: IPCOM000002255D
Original Publication Date: 1993-Feb-01
Included in the Prior Art Database: 2000-Sep-12
Document File: 5 page(s) / 11K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

G. Vaudreuil: AUTHOR

Abstract

Protocols for extending SMTP to pass 8bit characters have been defined [3] [4]. These protocols require that messages transported by the extended SMTP are to be encoded in MIME [1] [2]. Before work began on these protocols, several SMTP implementations adopted ad-hoc mechanisms for sending 8bit data. It is desirable for the extended SMTP environment and these ad hoc mechanisms interoperate. This document outlines the problems in this environment and an approach to minimizing the cost of transition from current usage of non-MIME 8bit messages to MIME.

This text was extracted from a ASCII Text document.
This is the abbreviated version, containing approximately 27% of the total text.

Network Working Group G. Vaudreuil

Request for Comments: 1428 CNRI

February 1993

Transition of Internet Mail from

Just-Send-8

to 8bit-SMTP/MIME

Status of this Memo

This RFC provides information for the Internet community. It does

not specify an Internet standard. Distribution of this memo is

unlimited.

Abstract

Protocols for extending SMTP to pass 8bit characters have been

defined [3] [4]. These protocols require that messages transported by

the extended SMTP are to be encoded in MIME [1] [2]. Before work

began on these protocols, several SMTP implementations adopted ad-hoc

mechanisms for sending 8bit data. It is desirable for the extended

SMTP environment and these ad hoc mechanisms interoperate. This

document outlines the problems in this environment and an approach to

minimizing the cost of transition from current usage of non-MIME 8bit

messages to MIME.

1. Terminology

RFC 821 defines a 7bit transport. A transport agent which does not

clear the high order bit upon receipt of octets with this bit set in

SMTP messages is called 8 bit transparent in this document. An

implementation of the general SMTP Extensions document [3] and the

8bit extensions protocol [4] which passes MIME messages using all 8

bits of an octet is called 8bit ESMTP. An implementation of extended

SMTP which does not accept 8bit characters is called 7bit ESMTP. A

gateway is defined to be a transport agent with User Agent authority

to alter or convert the content of a message.

2. The Problem

SMTP as defined in RFC 821 limits the sending of Internet Mail to

US-ASCII [5] characters. As the Internet has grown to include non-

English correspondents, the need to communicate with character sets

other than US-ASCII has prompted many vendors and users to extend

SMTP or RFC 822 to use non-ASCII character sets. Common approaches

are to send 7 bit national variant ISO 646 character sets over

current RFC822/SMTP, to extend SMTP and RFC822 to use 8bit ISO 8859

character sets, and to use proprietary PC character sets.

A third approach is used for Japanese mail. Japanese characters are

represented by pairs of octets with the high order bit cleared.

Switching between 14 bit character sets and 7 bit character sets is

indicated within the message by ISO 2022 escape sequences.

So long as these implementations can communicate without intermediate

transformations and have a loose private agreement on the use of a

specific character set without tagging, basic mail service can be

provided.

In the transition to the negotiated 8bit ESMTP/MIME environment, it

is important that mail sent by a currently non-conforming user can be

read by another non-conforming user. This existing functionality is

reduced by conve...