Re: Fw: [idn] IDNs in email message bodies

["Adam M. Costello" <amc@cs.berkeley.edu>]

Edmon <edmon@neteka.com> wrote:

> Yes they are used for both display and for "forming" replies, and it
> is during this "forming" process where the ACE conversion should take
> place.  The information itself within the field is for display and we
> should not confuse it with the actual protocol for transportation.

When someone replies to a message, the MUA extracts the email address
from the From: field, and hands this address to the MTA (which is often
built into the MUA), which then separates the domain from the local
part and does a DNS lookup on the domain.  If the MUA and MTA are not
IDN-aware, and the address in the From: field is a non-ACE IDN, then
this lookup will fail.

The header fields are not just for display.  Message headers are
primarily a protocol used by MUAs to communicate with other MUAs, just
as SMTP is a protocol used by MTAs to communicate with other MTAs, and
the message body is for the humans to communicate with other humans.
(Exceptions:  Several of the header fields, like From:, are of interest
to humans in addition to MUAs, and the Subject: field is only for the
humans.  The Received: fields are primarily for the MTAs.  MIME gets the
MUAs more involved with the message body.)

AMC