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RE: RFC 2822 email addresses in tag URIs

From: Walter Underwood <wunder@verity.com>
Date: Fri, 23 Sep 2005 10:01:07 -0700
To: "McDonald, Ira" <imcdonald@sharplabs.com>, "'Tim Kindberg'" <timothy@hpl.hp.com>, uri@w3.org
cc: sandro hawke <sandro@w3.org>
Message-ID: <53CD573DBCD68D8E0200CB8E@adsl-64-166-133-242.dsl.snfc21.pacbell.net>

--On September 23, 2005 8:19:41 AM -0700 "McDonald, Ira" <imcdonald@sharplabs.com> wrote:

> URI schemes should define canonicalization/normalization rules
> that allow correct comparisons based on user expectations.  No
> user expects that changing the case in an email address will
> cause it to differ in meaning.

They should. DNS hostnames are case-insensitive, but case-sensitivity
in the mailbox local-part is up to the implementation. Some systems are,
some aren't.

Interpretation of addresses is really part of RFC 2821, not RFC 2822,
but it is an essential part of internet mail.

>From section 2.4 of RFC 2821:

   ... That is,
   a command verb, an argument value other than a mailbox local-part,
   and free form text MAY be encoded in upper case, lower case, or any
   mixture of upper and lower case with no impact on its meaning.  This
   is NOT true of a mailbox local-part.  The local-part of a mailbox
   MUST BE treated as case sensitive.  Therefore, SMTP implementations
   MUST take care to preserve the case of mailbox local-parts.  Mailbox
   domains are not case sensitive.  In particular, for some hosts the
   user "smith" is different from the user "Smith".

Walter Underwood
Principal Software Architect, Verity
Received on Friday, 23 September 2005 17:00:48 UTC

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