As per Relevance of the word arbitrary, we have this rfc below:
Network Working Group J. Klensin, WG
Request for Comments: 1426 United Nations
N. Freed,
Innosoft International, Inc
M.
Dover Beach Consulting, Inc
E.
Network Management Associates, Inc
D.
The Branch
February 1993
SMTP Service
for 8bit-
Status of this
This RFC specifies an IAB standards track protocol for the
community, and requests discussion and suggestions for improvements
Please refer to the current edition of the "IAB Official
Standards" for the standardization state and status of this protocol
Distribution of this memo is unlimited
1.
This memo defines an extension to the SMTP service whereby an
content body containing octets outside of the US ASCII octet
(hex 00-7F) may be relayed using SMTP
2.
Although SMTP is widely and robustly deployed, various
have been requested by parts of the Internet community.
particular, a significant portion of the Internet community wishes
exchange messages in which the content body consists of a
message [3] containing arbitrary octet-aligned material. This
uses the mechanism described in [5] to define an extension to
SMTP service whereby such contents may be exchanged. Note that
extension does NOT eliminate the possibility of an SMTP
limiting line length; servers are free to implement this
but nevertheless set a line length limit no lower than 1000 octets
3. Framework for the 8bit MIME Transport
The 8bit MIME transport extension is laid out as follows
Klensin, Freed, Rose, Stefferud & Crocker [Page 1]
RFC 1426 SMTP 8bit-MIMEtransport February 1993
(1) the name of the SMTP service extension defined here
8bit-MIMEtransport
(2) the EHLO keyword value associated with the extension
8BITMIME
(3) no parameter is used with the 8BITMIME EHLO keyword
(4) one optional parameter using the keyword BODY is added
the MAIL FROM command. The value associated with
parameter is a keyword indicating whether a 7bit
(in strict compliance with [1]) or a MIME message (
strict compliance with [3]) with arbitrary octet
is being sent. The syntax of the value is as follows
using the ABNF notation of [2]:
body-value ::= "7BIT" / "8BITMIME
(5) no additional SMTP verbs are defined by this extension
and
(6) the next section specifies how support for the
affects the behavior of a server and client SMTP
4. The 8bit-MIMEtransport service
When a client SMTP wishes to submit (using the MAIL command)
content body consisting of a MIME message containing
octet-aligned material, it first issues the EHLO command to
server SMTP. If the server SMTP responds with code 250 to the
command, and the response includes the EHLO keyword value 8BITMIME
then the server SMTP is indicating that it supports the extended
command and will accept MIME messages containing arbitrary octet
aligned material
The extended MAIL command is issued by a client SMTP when it
to transmit a content body consisting of a MIME message
arbitrary octet-aligned material. The syntax for this command
identical to the MAIL command in [1], except that a BODY
must appear after the address
The complete syntax of this extended command is defined in [5].
esmtp-keyword is BODY and the syntax for esmtp-value is given by
syntax for body-value shown above
The value associated with the BODY parameter indicates whether
content body which will be passed using the DATA command consists
a MIME message containing some arbitrary octet-aligned
Klensin, Freed, Rose, Stefferud & Crocker [Page 2]
RFC 1426 SMTP 8bit-MIMEtransport February 1993
("8BITMIME") or is encoded entirely in accordance with [1] ("7BIT").
A server which supports the 8-bit MIME transport service
shall preserve all bits in each octet passed using the DATA command
Naturally, the usual SMTP data-stuffing algorithm applies so that
content which contains the five-character sequence
or a content that begins with the three-character sequence
does not prematurely terminate the transfer of the content. Further
it should be noted that the CR-LF pair immediately preceeding
final dot is considered part of the content. Finally, although
content body contains arbitrary octet-aligned material, the length
each line (number of octets between two CR-LF pairs), is
subject to SMTP server line length restrictions (which may allow
few as 1000 octets on a single line).
Once a server SMTP supporting the 8bit-MIMEtransport
extension accepts a content body containing octets with the high
order (8th) bit set, the server SMTP must deliver or relay
content in such a way as to preserve all bits in each octet
If a server SMTP does not support the 8-bit MIME transport
(either by not responding with code 250 to the EHLO command, or
not including the EHLO keyword value 8BITMIME in its response),
the client SMTP must not, under any circumstances, attempt
transfer a content which contains characters outside the US
octet range (hex 00-7F).
A client SMTP has two options in this case: first, it may
a gateway transformation to convert the message into valid 7bit MIME
or second, or may treat this as a permanent error and handle it
the usual manner for delivery failures. The specifics of
transformation from 8bit MIME to 7bit MIME are not described by
RFC; the conversion is nevertheless constrained in the
ways
(1) it must cause no loss of information; MIME
encodings must be employed as needed to insure this
the case,
(2) the resulting message must be valid 7bit MIME
Klensin, Freed, Rose, Stefferud & Crocker [Page 3]
RFC 1426 SMTP 8bit-MIMEtransport February 1993
5. Usage
The following dialogue illustrates the use of the 8bit-
service extension
S: connection on TCP port 25>
C: connection to server
S: 220 dbc.mtview.ca.us SMTP service
C: EHLO ymir.claremont.
S: 250-dbc.mtview.ca.us says
S: 250 8
C: MAIL FROM: BODY=8
S: 250 ... Sender and 8BITMIME
C: RCPT TO:
S: 250 ... Recipient
C:
S: 354 Send 8BITMIME message, ending in CRLF.CRLF
...
C: .
S: 250
C:
S: 250
6. Security
This RFC does not discuss security issues and is not believed
raise any security issues not already endemic in electronic mail
present in fully conforming implementations of [1].
7.
This document represents a synthesis of the ideas of many people
reactions to the ideas and proposals of others. Randall Atkinson
Craig Everhart, Risto Kankkunen, and Greg Vaudreuil contributed
and text sufficient to be considered co-authors. Other
suggestions, text, or encouragement came from Harald Alvestrand,
Conklin, Mark Crispin, Frank da Cruz, 'Olafur Gudmundsson,
Hedeland, Christian Huitma, Neil Katin, Eliot Lear, Harold A
Miller, Keith Moore, Dan Oscarsson, Julian Onions, Neil Rickert,
Wagner, Rayan Zachariassen, and the contributions of the entire
SMTP Working Group. Of course, none of the individuals
necessarily responsible for the combination of ideas
here. Indeed, in some cases, the response to a particular
was to accept the problem identification but to include an
different solution from the one originally proposed
Klensin, Freed, Rose, Stefferud & Crocker [Page 4]
RFC 1426 SMTP 8bit-MIMEtransport February 1993
8.
[1] Postel, J., "Simple Mail Transfer Protocol", STD 10, RFC 821,
USC/Information Sciences Institute, August 1982.
[2] Crocker, D., "Standard for the Format of ARPA Internet
Messages", STD 11, RFC 822, UDEL, August 1982.
[3] Borenstein, N., and N. Freed, "Multipurpose Internet
Extensions", RFC 1341, Bellcore, Innosoft, June 1992.
[4] Moore, K., "Representation of Non-ASCII Text in Internet
Headers", RFC 1342, University of Tennessee, June 1992.
[5] Klensin, J., WG Chair, Freed, N., Editor, Rose, M., Stefferud
E., and D. Crocker, "SMTP Service Extensions" RFC 1425,
Nations University, Innosoft International, Inc., Dover
Consulting, Inc., Network Management Associates, Inc., The
Office, February 1993.
[6] Partridge, C., "Mail Routing and the Domain System", RFC 974,
BBN, January 1986.
9. Chair, Editor, and Authors'
John Klensin, WG
United Nations
PO Box 500, Charles Street
Boston, MA 02114-0500
Phone: +1 617 227 8747
Fax: +1 617 491 6266
Email: klensin@infoods.unu.
Ned Freed,
Innosoft International, Inc
250 West First Street, Suite 240
Claremont, CA 91711
Phone: +1 909 624 7907
Fax: +1 909 621 5319
Email: ned@innosoft.
Klensin, Freed, Rose, Stefferud & Crocker [Page 5]
RFC 1426 SMTP 8bit-MIMEtransport February 1993
Marshall T.
Dover Beach Consulting, Inc
420 Whisman
Moutain View, CA 94043-2186
Phone: +1 415 968 1052
Fax: +1 415 968 2510
Email: mrose@dbc.mtview.ca.
Einar A.
Network Management Associates, Inc
17301 Drey
Huntington Beach, CA, 92647-5615
Phone: +1 714 842 3711
Fax: +1 714 848 2091
Email: stef@nma.
David H.
The Branch
Email: dcrocker@mordor.stanford.
Klensin, Freed, Rose, Stefferud & Crocker [Page 6]
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