Subject: [Emailcore] Delivered-To issues

From: Dave Crocker <[email-masked]>
Date: Thu, 31 Dec 2020 13:09:16 -0800

I think I've got enough information to formulate an initial draft, for 
people to shoot at, except for:

1.  Why a separate header field, rather than Received's FOR clause?

2. What should it say about delivery to multiple recipients?

    The easiest -- and probably most problematic, for some systems that 
share access to a single copy of the message -- is to say it must only 
contain one address.  If the spec says something else, what should it 
be, and why?

3. ?

d/
-- 
Dave Crocker
Brandenburg InternetWorking
bbiw.net

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From: John C Klensin <[email-masked]>
Date: Thu, 31 Dec 2020 16:43:28 -0500

--On Thursday, December 31, 2020 13:09 -0800 Dave Crocker
<[email-masked]> wrote:

> I think I've got enough information to formulate an initial
> draft, for people to shoot at, except for:
> 
> 
>     The easiest -- and probably most problematic, for some
> systems that share access to a single copy of the message --
> is to say it must only contain one address.  If the spec says
> something else, what should it be, and why?
> 
> 
> 3. ?

My candidate for 3 would be whether the contents of the header
field reflect the last address seen by SMTP (i.e., presumably
the RCPT address --or more than one which comes back to your #2
-- at the time of handoff to the final delivery server) or the
address at the time of delivery to the actual recipient mailbox.

I look forward to seeing the draft.

    john

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From: "John Levine" <[email-masked]>
Date: 31 Dec 2020 17:33:39 -0500

>1.  Why a separate header field, rather than Received's FOR clause?

What jck said, the mailbox into which a message is delivered often has
a different name from what was in the RCPT TO.  That's particularly
likely on systems that handle mail for multiple domains.

>contain one address.  If the spec says something else, what should it 

I think at this point we'd be making stuff up because I've never seen a
Delivered-To for multiple recipients.  I'm inclined to follow what sec
4.4 of RFC5321 says and only report one recipient address.

R's,
John

---

From: Dave Crocker <[email-masked]>
Date: Thu, 31 Dec 2020 14:45:23 -0800

> likely on systems that handle mail for multiple domains.

with apologies to all, for my reading comprehension, limitations, but 
would someone point to the place in RFC 5321 where the semantics of the 
FOR clause are explained, and especially in terms of it's coming from a 
RCPT TO?

The language in Section 4.4, in the third bullet, might be claimed to 
imply this, but it doesn't actually say it.  And that bullet does not 
have a focus of defining the parameter's semantics.

d/