Re: [EAI] double angle brackets

[Ernie Dainow <edainow at ca.afilias.info>]

Shawn Steele wrote:
> > 	* non-EAI, support for multiple "From:": will accept
> > 	both and probably discard the i18n email address.
> >     
>
> That's an interesting assumption.  Presumably I could also reject the entire message since I have no clue how to parse the address.
> 	
>   
> > 	* non-EAI, no support for multiple "From:": Will reject
> > 	either both addresses or the second one.  If one is
> > 	accepted, probably the first one (which should probably
> > 	be the ASCII address) will probably be used.  If both
> > 	are rejected, then nothing much is lost compared to the
> > 	failed downgrade case -- especially if you remember that
> > 	an EAI envelope is unlikely to reach a non-EAI system.
> >     
>
> Ditto.
>   
For non-EAI, downgrade would remove the i18n email address, so From does 
not have multiple addresses.
> 	
>   
> > 	* EAI compliant system: will support multiple "From:"
> > 	because the spec will require it.  
> >     
>
> I still can't tell that they're a pair.  It could be intentionally from 2 different people, one of which has an EAI address, but the other has an ASCII address, and we don't know (or didn't bother to mention) what the EAI address user's downgrade address is.
>
> So an EAI compliant system that "assumed" that "From: Unicode, ASCII" was EAI would not bother replying to the ASCII address, &/or it would 
>
>   
This case would have a Reply-To with the EAI address, so the multiple 
From fields are not used. The reply is composed to the address(es) 
contained in the Reply-To and none of the From headers (see RFC 5322). I 
have tested this with a web mail client and a widely used windows/linux 
email client. From: had two addresses and Reply-To: had a third. When 
replying to such an email, both clients composed mail with To: that 
contained the Reply-To: address only.

Based on this, I expect that most email clients that are upgraded to 
support EAI will actually support the proposal (repeated below) without 
requiring any further work.
   From: EAI-addr, ASCII-addr
   Reply-To: EAI-addr
(where the EAI-addr gets dropped in Downgrade)

> Besides, if this was reasonable for From, what about To: or CC: or Reply-To:?  Presumably I could mail it to other EAI users as well, so how does a recipient respond?  How would one reliably match up the pairs?
>
> Also, presumably I know my own downgrade address, but am I going to know all of the downgrade addresses for everyone on To: (or hopefully Bcc:) that I'm forwarding a joke to?
>   
As part of the downgrade simplification, we are proposing to drop 
support for downgrade of forward pointing addresses such as To:, Cc:.If 
someone gives you an EAI address, the assumption is that their email 
system can receive EAI email.If their system cannot receive EAI email, 
it is a 'configuration' error on their end and they shouldn't be giving 
out an EAI address until they are ready to receive such mail.

> I remain unconvinced that this solves enough downgrade problems completely enough to be interesting.
>
> -Shawn
>
>