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Re: Testing UTF-8 email addresses

From: John C Klensin <john+w3c@jck.com>
Date: Wed, 29 May 2013 11:23:03 -0400
To: Leif Halvard Silli <xn--mlform-iua@xn--mlform-iua.no>, Paul Deuter <pdeuter@zendesk.com>
cc: www-international@w3.org
Message-ID: <C09E0D70E9FD1F4B8984517D@JcK-HP8200.jck.com>


--On Wednesday, May 29, 2013 16:40 +0200 Leif Halvard Silli
<xn--mlform-iua@xn--mlform-iua.no> wrote:

> Just a question - to you or whoever: Is "UTF-8 email
> address" something  other than e-mail addresses where the
> domain name is an IDN? Or does it  related to the part before
> the @-character? 

The latter (called the "local part" in email-speak.

See RFCs 6530-6533 and 6855-6858.

Note that there turns out to be a lot more to this than just
handling UTF-8 in addresses.  In particular, the addresses
affect header fields as well as the envelope (and
address-specific header fields), message encapsulation issues,
and the need to have transition strategies for sites and clients
that can't handle the extended addresses.

> Btw: As a person who has personal experience over some years
> with using  the former - an e-mail address with an IDN domain
> name, I find that the  only trouble I have is when some online
> service asks me to enter my  email address: It ought to be
> possible to type foo@målform.example.com  - in decoded form.
> But I constantly have to use the IDN coded form - 
> foo@xn--mlform-iua.example.com.

Because the syntax rules in RFC 5321 (and 821 and 2821) very
explicitly prohibit non-ASCII characters in an email address
("mailbox name") you will find that many mail clients reject
such things.  Of course, if the client sees non-ASCII characters
in the domain part of the address and converts the appropriate
labels to A-Labels as specified for IDNA before transmitting the
message, the inter-host email system (and the recipient) don't
need to know what you entered.   But non-ASCII local parts or
transmission of messages with non-ASCII UTF-8 addresses or
headers requires the extensions specified in the RFCs identified
above.

    john
Received on Wednesday, 29 May 2013 15:23:41 UTC

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