SMTP Service Extension for 8bit-MIMEtransport (RFC1652)
Original Publication Date: 1994-Jul-01
Included in the Prior Art Database: 2000-Sep-12
Internet Society Requests For Comment (RFCs)
J. Klensin: AUTHOR [+5]
This memo defines an extension to the SMTP service whereby an SMTP content body consisting of text containing octets outside of the US- ASCII octet range (hex 00-7F) may be relayed using SMTP.
Network Working Group J. Klensin, WG Chair
Request for Comments: 1652 MCI
Obsoletes: 1426 N. Freed, Editor
Category: Standards Track Innosoft
Dover Beach Consulting, Inc.
Network Management Associates, Inc.
Silicon Graphics, Inc.
SMTP Service Extension for 8bit-MIMEtransport
Status of this Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
This memo defines an extension to the SMTP service whereby an SMTP
content body consisting of text containing octets outside of the US-
ASCII octet range (hex 00-7F) may be relayed using SMTP.
Although SMTP is widely and robustly deployed, various extensions
have been requested by parts of the Internet community. In
particular, a significant portion of the Internet community wishes to
exchange messages in which the content body consists of a MIME
message  containing arbitrary octet-aligned material. This memo
uses the mechanism described in  to define an extension to the
SMTP service whereby such contents may be exchanged. Note that this
extension does NOT eliminate the possibility of an SMTP server
limiting line length; servers are free to implement this extension
but nevertheless set a line length limit no lower than 1000 octets.
Given that this restriction still applies, this extension does NOT
provide a means for transferring unencoded binary via SMTP.
2. Framework for the 8bit MIME Transport Extension
The 8bit MIME transport extension is laid out as follows:
(1) the name of the SMTP service extension defined here is
(2) the EHLO keyword value associated with the extension is
(3) no parameter is used with the 8BITMIME EHLO keyword;
(4) one optional parameter using the keyword BODY is added to
the MAIL FROM command. The value associated with this
parameter is a keyword indicating whether a 7bit message
(in strict compliance with ) or a MIME message (in
strict compliance with ) with arbitrary octet content
is being sent. The syntax of the value is as follows,