Subject: Re: [EAI] Consensus Result - trace fields and RFC5336bis

From: Jiankang Yao <[email-masked]>
Date: Mon, 4 Jul 2011 20:57:59 +0800

----- Original Message -----
From: "Joseph Yee" <[email-masked]>
To: <[email-masked]>
Sent: Monday, July 04, 2011 6:01 PM
Subject: [EAI] Consensus Result - trace fields and RFC5336bis

> All,
>
> Following discussion, the WG agreed that message under SMTP without the EAI parameter at MAIL FROM must conform to RFC5321 regardless the server's capability.  Trace field values must conform to RFC5321, whether it's an initial submission or relay.
>
> For message under SMTP with EAI parameter at MAIL FROM, an EAI-capable client SHOULD send messages what require EAI functionality in UTF-8 form to servers that do support EAI functionality.  Trace field values (the domain name) in the "from" clause of "Received:" should use U-label.
>
>

In this case, only the "from" clause of "Received:"  use u-label?

other clauses such as "for" still use A-label?

Jiankang Yao

---

From: John C Klensin <[email-masked]>
Date: Mon, 04 Jul 2011 09:24:43 -0400

--On Monday, July 04, 2011 20:57 +0800 Jiankang Yao
<[email-masked]> wrote:

>...
>> For message under SMTP with EAI parameter at MAIL FROM, an
>> EAI-capable client SHOULD send messages what require EAI
>> functionality in UTF-8 form to servers that do support EAI
>> functionality.  Trace field values (the domain name) in the
>> "from" clause of "Received:" should use U-label.

> other clauses such as "for" still use A-label?

Personal opinion (but I think consistent with the WG
discussion): once one starts putting any UTF-8-encoded material
(U-labels or text) into the headers, there is little reason to
try to say "use it here, but not there".  If the receiver can
handle that material, then it can handle it; if it cannot, it is
in big trouble and whether that trouble is about one subfield or
about several makes no difference.

So, if U-labels are used in "Received ...from" clauses, there is
not reason at all to require that A-labels be used in "for"
clauses and many reasons to prefer U-labels.

Note in addition that "for" with A-labels would be useful only
in what we've called the ASCII@IDN case.  For the non-ASCII@IDN
case, UTF-8 is going to appear in the local-part so there is no
advantage at all to avoiding it in the domain-part.  FWIW, I
believe that, in practical terms, the ASCII@IDN case will be
fairly rare. If an IDN-style domain name is used for the
destination mail server, people will want, and we will see,
EAI-style addresses in the local-part.   An exception might
arise for a given person trying to maintain both EAI and ASCII
local-part addresses but, if I were writing that particular bit
of guidance today, I'd recommend that user configured alternate
addresses be in domains consisting entirely of LDH labels.  The
many discussions in the WG in the last several weeks illustrate
why: if one has a 5321-conformant message, one is better off
making sure that it stays that way rather than having A-labels
converted to U-labels by an enthusiastic intermediary and then
having the message bounced somewhere downstream.  But, again,
that is just my opinion.

    john

---

From: "John Levine" <[email-masked]>
Date: 4 Jul 2011 17:41:33 -0000

>about several makes no difference.

Agreed.  I'd offer language but it appears that other people
have it under control.

R's,
John