Re: Question: UseSTD3ASCIIRules on RHS of IMA

Roy Badami <[email protected]> writes:

>    Informative text doesn't hurt, I guess, but IMAA shouldn't make
>    normative statements about this IMHO.
>
>    All application must already know the answer to this problem, as the
>    same problem existed before IDNA.  If the RFCs are unclear, that
>    should be fixed independently of IMAA.
>
> This is what IDNA says, but I'm not sure it's true.  I doubt most mail
> software knows the answer to this problem; I suspect that most MUAs
> simply pass the address to the MTA and see what happens, and that most
> MTAs simply pass the domain to the resolver and see what happens.
>
> In the absence of an RFC-mandated requirement to validate the domain,
> it could be argued that this is the correct thing to do in terms of the
> robustness principle, even if the domain name contains characters that
> are technically illegal.
>
> However, with IMAs, the MUA has to explicitly invoke IDNA, and it
> hence has to choose a value for the UseSTD3ASCIIRules flag.  It isn't
> absolutely clear to me what the correct value of this flag is (though
> it may be clear to others), and it's highly desirable that IMAA
> implementations behave consistently.  I don't see why normative text
> must be ruled out.

IDNA suggests that applications that simply passed things on before
should not set the flag, and applications that enforces hostname
restrictions today should set the flag.  Application have made a
decision, conscious or not.  I'm not sure I see any need to enforce
anything with regard to this more than already is, and in particular
not how IMAA would be the right place for it.

,----
| 3) For each label, decide whether or not to enforce the restrictions on
| ASCII characters in host names [STD3]. (Applications already faced this
| choice before the introduction of IDNA, and can continue to make the
| decision the same way they always have; IDNA makes no new
| recommendations regarding this choice.) If the restrictions are to be
| enforced, set the flag called "UseSTD3ASCIIRules" for that label.
`----