Re: [EAI] Localpart normalization (was Re: Downgrade Design Team Discussion Results Released)

[Harald Alvestrand <[e-mail]>]

Alexey Melnikov wrote:
> As a side note, one of the things suggested by the EAI downgrade 
> design team should be further discussed and should be coordinated with 
> the NewPrep BOF:
>
> YAO Jiankang wrote:
>> The design team also noted that an informational RFC regarding
>> selection of addresses (both Unicode and ASCII) would be
>> helpful, that clients SHOULD use Unicode Normalization Form C,
>> and that servers MUST use NFC.
>>   
> Whatever normalization we recommend, it should be consistent with 
> handling of nodes in XMPP (NodePrepBis) and SASLPrepBis. 
Note:
we should be careful what we mean here when we say "MUST use NFC".

I read it as "everyone should expect mail to two left-hand-side whose 
name canonicalizes to the same string under NFC to end up in the same 
mailbox".

That's no guarantee that mail to Unicode(R with ring around it) and 
UnicodeR will NOT end up in the same mailbox. Any server can apply 
additional normalizations at will to localparts that it's responsible for.

The difference between putting NFC and NFKC in the sentence above is 
that no intermediate server, who's merely passing along the message, can 
make the assumption that (R with ring around it) and (R) are equivalent.

                        Harald