On Mar 28, 2014, at 10:52 AM, "Neely, Lee" < email@hidden> wrote: All- I was questioning Apple’s decision to consider the left, or Local part of the Email Address as case-sensitive, so I spent time following the RFCs. I did some checking, and Apple may be allowed to use a case-sensitive check for the left side of an email address. I followed the RFC’s back to try and figure out the requirements. I started with RFC 5751, http://tools.ietf.org/html/rfc5751- the S/MIME standard - it points to RFC 5750 (S/MIME 3.2) which references RFC 5280 – X.509 standard which references RFC 2821
– which ultimately states the Local-part of the SMTP email address May be case sensitive. _SO_ Apple is following the allowances of RFC 2821.
5321 says:
Verbs and argument values (e.g., "TO:" or "to:" in the RCPT command
and extension name keywords) are not case sensitive, with the sole
exception in this specification of a mailbox local-part (SMTP
Extensions may explicitly specify case-sensitive elements). 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. 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. In particular, for some hosts, the user
"smith" is different from the user "Smith". However, exploiting the
case sensitivity of mailbox local-parts impedes interoperability and
is discouraged. Mailbox domains follow normal DNS rules and are
hence not case sensitive.
Without reading 5380 (+6818) on this point, I think some of the issues fall between standards. It seems clear that the people writing the mail standards feel it's a Really Bad Idea™ to make case matter in email addresses, but you'd bloody well better make it *possible* to matter.
The care in the wording of the above spec suggests to me that there was some serious discussion of the issue. That suggests to me that someone wanting to change the spec will need to research the concerns of the people involved at the time and make sure they are still satisfied by any new spec. It also means building consensus for new language will take a lot of effort. (-: Am I repeating T. Miller? ;-)
As for what Apple does: I think they are within the spec. However I also think most people think what Apple is doing is a Really Bad Idea™ because it "impedes interoperability".
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OK, I just went back and glanced through 5380 and found the following interesting sentence in the Security Considerations section:
Implementers should not
include an email address in the emailAddress attribute if the email
server that hosts the email address treats the local-part of email
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