From: Otto Stolz (Otto.Stolz@uni-konstanz.de)
Date: Tue Dec 17 2002 - 07:28:00 EST
Dear all,
Barry Caplan had written:
> SMTP [...] is not 8 bit clean. It is very
> clear in the RFCs that only 7bit data is allowed "over the wire".
Stephane Bortzmeyer wrote:
> All these extensions are referenced in the same RFC, 2821, which is
> the authoritative one about SMTP.
As of November 2002, RFC 2821 is still a Proposed Standard, and RFC 821
is the Standard Protocol (cf. <http://rfc.sunsite.dk/rfc/rfc3300.html>).
> The most important for us is 8BITMIME:
Section 2.3.1 of RFC 2821, the proposed standard, says:
| The content is textual in nature, expressed using the US-ASCII
| repertoire [1]. Although SMTP extensions (such as "8BITMIME" [20])
| may relax this restriction for the content body,
Stephane Bortzmeyer quoted section 2.4 of RFC 2821:
> Eight-bit message content transmission MAY be requested of the server
> by a client using extended SMTP facilities, notably the "8BITMIME"
> extension [20]. 8BITMIME SHOULD be supported by SMTP servers.
"SHOULD" does definitely not mean the same thing as "MUST".
An SMTP server does not have to support 8-bit MIME mail.
And the remainder of the quoted paragraph requests proper MIME
headers for 8-bit text:
| However, it MUST not be construed as authorization to transmit
| unrestricted eight bit material. 8BITMIME MUST NOT be requested
| by senders for material with the high bit on that is not in MIME
| format with an appropriate content-transfer encoding; servers
| MAY reject such messages.
Barry Caplan had written:
> But for arbitrary email from one address to another, you can't rely on it.
Stephane Bortzmeyer wrote:
> I send Latin-1 (ISO 8859-1) emails for more than ten years (and
> without using quoted-printable or other similar hacks) to
> French-speaking people in various parts of the world and I'm still
> waiting for an actual problem.
Mere luck, I'd say, but no proof at all.
I have seen many messages, originally in ISO-8859-1-encoded French,
that got the high-bit of every accented character chopped off, thus
replacing "é" with "i", "î" with "n", and so forth. And even more mail
in German, distorted in a similar way. This has provoked an entry in
my E-Mail FAQ: <http://www.systems.uni-konstanz.de/EMAIL/FAQ.php#SMTP-73>.
Of course, more and more SMTP servers support 8-bit MIME, and many
take the pains to transform 8-bit MIME to some transfer-encoding
supported by the receiving server. If you are located behind a server
that recodes your 8-bit mail, you cannot claim that 8-bit mail is
supported everywhere; you can only claim that your server compensates
for the incompatibility of your MUA and the world at large.
Best wishes,
Otto Stolz
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