Re: [EAI] mail bounce versus punycode conversion
"Jiankang YAO" <yaojk@cnnic.cn> Tue, 10 August 2010 05:31 UTC
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From: Jiankang YAO <yaojk@cnnic.cn>
To: Ernie Dainow <edainow@ca.afilias.info>, John C Klensin <klensin@jck.com>
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Subject: Re: [EAI] mail bounce versus punycode conversion
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based on the ietf 78 eai meeting, I have updated it to the following text: If a server advertises UTF8SMTP and the client does not recognize the extension, the client may send a regular message [RFC5321] and [RFC5322]. In this case, the client may continue to use the [RFC5890] to transform the domain portion of an address to A-label [RFC5890]. If the email address is in the format of ASCII@non-ASCII, the legacy SMTP servers MUST reject the message with the ASCII@non-ASCII if the non-ASCII domain part is not transformed into the format of A-label by the client. UTF8SMTPbis servers MUST recognize and decode the ACE label(s) as appropriate. Jiankang Yao ----- Original Message ----- From: "Ernie Dainow" <edainow@ca.afilias.info> To: "John C Klensin" <klensin@jck.com> Cc: <ima@ietf.org> Sent: Tuesday, July 13, 2010 8:59 PM Subject: Re: [EAI] mail bounce versus punycode conversion > On 7/13/2010 1:53 AM, John C Klensin wrote: >> >> --On Monday, July 12, 2010 17:17 -0400 Ernie Dainow >> <edainow@ca.afilias.info> wrote: >> >> >>> A message to mailbox<ASCII@non-ASCII> will bounce if the >>> UTF8SMTPbis extension is not supported by an MTA. According to >>> rfc5336bis, this will not be done by an MTA. This is not >>> obvious behavior, since it is fairly trivial to do a punycode >>> conversion of the domain part so that the address is all >>> ASCII. Many users are familiar with web browsers that do this >>> conversion and may expect similar behavior in email. >>> >> Speaking for myself only, this is actually one of the difficult >> cases I was sort of alluding to in an earlier note today. >> >> Please review draft-iab-idn-encoding (-03 was posted yesterday). >> If one has a system in which any string in a multi-target name >> resolution slot is passed to a common name resolution interface, >> then it probably will not be possible to prevent an >> <ASCII@non-ASCII> string from being resolved, with or without >> EAI. Similarly, if a system identifies the domain part as being >> an IDNA-aware domain name slot,<ASCII@non-ASCII> might be >> turned into<ASCII@A-label.A-label....> before the mail-specific >> software actually gets its hands on it and subsequently treated >> as an all-ASCII address. >> >> It is plausible to put<ASCII@non-ASCII> outside the scope of an >> EAI standard if the extension isn't specified. That follows >> from the observation that, if the extension is not specified, >> everything (ASCII and non-ASCII alike) is outside the scope of >> the standard. But requiring message rejection in one of those >> cases is not reasonable: servers who do not announce the >> extension are bound only by the rules of RFC 5321 and friends. >> Those specifications are specific about what must be accepted >> but deliberately not specific about what must be rejected. >> >> >> >>> To reinforce that this is a failure case, we should add the >>> following example to section 4.4 of rfc5335bis-00. >>> >>> <ASCII@non-ASCII> >>> ; message will bounce if UTF8SMTPbis extension is not >>> supported. An MTA will not convert >>> ; the domain part to ASCII, but this may be done by >>> an MUA or submission server (MSA). >>> >> The strongest thing that can be said, ideally with a citation of >> 5321, is something like: >> >> <ASCII@non-ASCII> >> ; if theUTF8SMTPbis extension is not supported, >> ; the MTA is required to be SMTP [RFC 5321]-compliant >> ; only. Such an MTA is not required to >> ; convert the domain part to from U-label form to >> ; A-label form. If it does not, the message may be >> ; rejected or simply not delivered. Similarly, >> ; if theUTF8SMTPbis extension is not supported, an >> ; MUA or submission server (MSA) may perform conversions >> ; to A-label form, but is not required to do so. >> > > According to section 3.2 in 5336bis-00, <ASCII@non-ASCII> is an > internationalized address and can't be submitted to an MTA that does not > support UTF8SMTPbis. An MTA cannot rewrite such a header so the message > must be rejected. If we want to allow an MTA to do punycode conversion, > the following paragraph in 5336bis-00 needs to be revised. > > 1. If and only if the SMTP client (sender) is a Message Submission > Server ("MSA") [RFC4409], it MAY, consistent with the general > provisions for changes by such servers, rewrite the envelope, > headers, or message material to make them entirely ASCII > >> >> Note that the IRI spec makes this even more difficult because >> >> mailto:ASCII@non-ASCII >> >> is at least as likely to be converted into >> >> mailto:ASCII@%-encoded-UTF-8 >> >> as into >> >> mailto:ASCII@A-label... >> >> john >> >> > > _______________________________________________ > IMA mailing list > IMA@ietf.org > https://www.ietf.org/mailman/listinfo/ima
- [EAI] mail bounce versus punycode conversion Ernie Dainow
- Re: [EAI] mail bounce versus punycode conversion John C Klensin
- Re: [EAI] mail bounce versus punycode conversion Shawn Steele
- Re: [EAI] mail bounce versus punycode conversion John C Klensin
- Re: [EAI] mail bounce versus punycode conversion Ernie Dainow
- Re: [EAI] mail bounce versus punycode conversion Joseph Yee
- Re: [EAI] mail bounce versus punycode conversion John C Klensin
- Re: [EAI] mail bounce versus punycode conversion John C Klensin
- Re: [EAI] mail bounce versus punycode conversion Ernie Dainow
- Re: [EAI] mail bounce versus punycode conversion Shawn Steele
- Re: [EAI] mail bounce versus punycode conversion Shawn Steele
- Re: [EAI] mail bounce versus punycode conversion Jiankang YAO
- Re: [EAI] mail bounce versus punycode conversion Ernie Dainow
- Re: [EAI] mail bounce versus punycode conversion Shawn Steele
- Re: [EAI] mail bounce versus punycode conversion Jiankang YAO
- Re: [EAI] mail bounce versus punycode conversion John C Klensin
- Re: [EAI] mail bounce versus punycode conversion Shawn Steele
- Re: [EAI] mail bounce versus punycode conversion John C Klensin
- Re: [EAI] mail bounce versus punycode conversion Shawn Steele
- Re: [EAI] mail bounce versus punycode conversion Joseph Yee
- Re: [EAI] mail bounce versus punycode conversion Shawn Steele