Re: [EAI] double angle brackets

["Charles Lindsey" <chl at clerew.man.ac.uk>]

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it could still say "this feature may well be withdrawn in a future version  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).

--
Charles H. Lindsey ---------At Home, doing my own thing------------------------
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