On Fri, 04 Sep 2009 22:46:26 +0100, Ernie Dainow
<edainow at ca.afilias.info> wrote:
One of the key goals in simplifying Downgrade is to drop the
double angle bracket notation, due to compatibility and
security concerns. There have been a few email threads on
this. I think the following summarizes the current thinking.
Dropping double angle brackets on Recipient addresses is part
of the downgrade simplification to not support downgrade of
forward pointing addresses (considering these cases as
configuration errors).
To replace double angle brackets for the Sender, John Klensin
proposed using multiple From fields. SM amended this with
Reply-To to specify the preferred address, as in
From: EAI-addr, ASCII-addr
Reply-To: EAI-addr
where the EAI-addr gets dropped in Downgrade.
I did some (non-EAI) tests of multiple From fields with
Reply-To on two different email systems and both worked as
expected. This looks like an elegant solution.
Yes, but the interesting case is multiple fields in Reply-To.
Normally, these will cause the reply to go to _both_ (but if
one is utf-8 and one is ascii, then the utf-8 might fail).
If we retain the double angle brackets, then one could still
say, in the Reply-To, "please reply to my utf-8 address if
possible, but if your system (or some intermediate server that
knows how to downgrade) can't do that, then please reply to my
ascii address".
I would expect that to be the commonest (and most useful)
situation in which those double angle brackets will appear in
practice.
So my preference would be to retain them, at least so long as
these remain Experimental documents. If the eventual Standard
still retains them, then it could still say "this feature may
well be withdrawn in a future version of this standard" (with
the intent to do so when utf-8 has become so widely
implemented that it is no longer needed).
