8-bit MIME (was: Documenting in Tamil Computing)

From: Otto Stolz (Otto.Stolz@uni-konstanz.de)
Date: Tue Dec 17 2002 - 07:28:00 EST

  • Next message: Stephane Bortzmeyer: "Re: 8-bit MIME (was: Documenting in Tamil Computing)"

    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 "" with "i", "" 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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