Punycode & IMA/EAI

Shawn Steele Shawn.Steele at microsoft.com
Thu May 15 23:36:20 CEST 2008

> > Consider also the IMA/EAI UTF-8 effort.  Clients that get a
> > pretty UTF-8 name aren't going to be able to process that
> > name if they can't do the punycode conversion to do the DNS
> > query because they're on the wrong version of IDN.  Sure,
> > they can (hopefully) use the fallback address, but I suspect
> > that'll have a human readable name, not a punycode string.

> AFAIK that affects only the RHS (domain part), for the LHS
> (local part) knowing what the UTF-8 means is not essential:
> The MSA can be (again) a "smart host" wrt EAI, and clients
> aren't forced to support punycode if they can handle UTF-8.
> The same goes for say whois servers vs. whois clients.

That's kind of what I meant. The EAI specifies UTF-8 for the domain part, not punycode, so a mail server can't deliver the mail unless they know how to do the Punycode conversion (or their DNS API does it for them).  Therefore requiring unknown A-names resolve might enable a URL, but mail will still break.  If I own the domain that won't help me then.

- Shawn

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