Re: [ietf-smtp] New Mailing List to discuss email canonicalization?

On 4/15/2016 10:23 AM, Arnt Gulbrandsen wrote:
> John C Klensin writes:
> > Unless people propose to update RFC 5321 to eliminate a
> > requirement that has been in place from 821 and through 1123 and
> > 2821, I don't see that there is anything to discuss.  It seems
> > to me that the rules are very clear, i.e., that, except on the
> > final delivery SMTP server, two mailboxes are equal iff:
> >
> >  -- The domain parts are equal under DNS rules
> >     (case-independent for ASCII strings and U-label:A-label
> >     equivalence for IDNA strings)
> >  -- The local parts are equal if they are octet-by-octet
> >     identical.
> If you ask people to type in their address in a web form, the 
> addresses will largely be typed in by people whose email addresses are 
> case-insensitive, and many of them know it. Rather like their names 
> and street addresses, which have proper casing but not essential casing.
> You're suggesting that although the user may know the address to be 
> case-sensitive, the software used should absolutely not consider it 
> case-insensitive.
At the end of the day, I do not see a problem with the status-quo in the 
mail standards, i.e., "case-preserving: DO NOT MESS WITH IT".
If the user types fooBAR(_at_)example(_dot_)com, take that as input and don't 
change it. If it delivers, great. If it doesn't deliver, ask the user 
for something else that delivers.
It should not be any intervening software's job to change the user's 
/expressed preference/, except for the delivery MTA. Whether the 
delivery MTA delivers foobar@ and fooBAR@ to the same place or different 
placeds, that is the delivery MTA's choice, alone.
Why again is this so complicated?

>>
If you ask people to type in their address in a web form, the addresses 
will largely be typed in by people whose email addresses are 
case-insensitive,
<<

*Are* email addresses case-insensitive? This is not an essential 
property of an email address. You, as an implementer, user, sysadmin, 
can treat strings as case-insensitive or case-sensitive as you wish. But 
your choice does not impact how the delivery MTA treats it. Just because 
you treat a bag of bits as "your property" doesn't mean it becomes your 
property. Only the delivery MTA has a say in the matter, that matters 
for the primary purpose of an email address: to deliver electronic mail.
>>
Rather like their names and street addresses, which have proper casing 
but not essential casing.
<<

True of some nations and postal systems, but not all. Only the national 
postal system gets a final say in the matter. Ask China vs. the United 
States vs. Turkey: they have different rules for what characters will 
result in delivery to the same physical mailbox.
Sean

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