Re: [Emailcore] Delivered-To issues

[John C Klensin <[e-mail]>]

--On Saturday, January 2, 2021 14:37 +0000 Jeremy Harris
<[e-mail]> wrote:

> On 02/01/2021 13:48, Dave Crocker wrote:
>> Any site performing the delivery transition of
>> responsibility, from the MHS to the addressee's control,
>> slaps a Deliver-To: header field, with
>> that one address on it.
> 
>> delivery ... takes place /within/ the MDA
> 
> I think this implies that the address is site-meaningful and
> not
> necessarily externally-meaningful nor qualified.  For example,
> a message received with an envlope RCPT of
> "[e-mail]"
> is locally aliased to "fred", has "Deliver-To: fred" prepended
> and then added to fred's mailbox.

Thinking about the above comment and several others in this
thread, if "Envelope-to" actually has the semantics of "relevant
RCPT to associated with the current delivery" (Jeremy, I think
that is the case in exim, but please confirm), then it and
"Deliver-to" have different semantics and are processed at
different points in the delivery process -- the former by the
final MTA and the latter by the MDA.

Should we be defining both, making it clear that they are
different, and then making whatever recommendations seem
appropriate about which one (or both) should be provided?

    john