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Re: [ietf-smtp] How wrong is this EAI implementation

2020-06-20 16:03:51
John,

IIR (I have not gone back and reread the spec), conversion of
the domain name to A-labels is strongly discouraged at any point
prior to the MSA or MTA actually looking up the domain name so a
connection can be opened.  For message headers (including not
just the "From:" header field but trace fields, etc.), it is
even more strongly discouraged: the intent was "restricted UTF-8
all the way" and "making users look at A-labels is just looking
for trouble".  However, the intent with IDNA (and, I think, the
push for IRIs) was much the same, keeping internal forms and
users separated and the latter working with native-character
forms to the extent possible.  However, the specs recognized
that exceptional circumstances could arise and therefore stop
short of complete prohibitions.

I haven't thought it through but, somehow, converting domains in
backward-pointing addresses (what do they do to/with
"Reply-to:"?) seems more, rather than less, offensive than
forward-pointing ones.

So, again relying on memory, the behavior you describe is in bad
taste and almost certainly represents bad judgment, but may not
actually be non-conforming.  I'll leave the question of how far
on that spectrum an implementation needs to lie to be considered
"broken".

  john

--On Saturday, June 20, 2020 14:54 -0400 John R Levine
<johnl(_at_)taugh(_dot_)com> wrote:

I am poking at the widely used Roundcube web mail package.

One of my test addresses is 测试@电子邮件测试.中国

When I enter it into Roundcube as a username, it turns the
domain into a-labels,
测试@xn--5nqx41au4nqohsp3axcg.xn--fiqs8s and uses that as
the address in the From: line, and to authenticate to IMAP and
submission.  I can understand where that came from, but it
still seems wrong.

Addresses that I put on the To: line seem unmolested.

Regards,
John Levine, johnl(_at_)taugh(_dot_)com, Taughannock Networks,
Trumansburg NY
Please consider the environment before reading this e-mail.
https://jl.ly




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