Subject: [Emailcore] Postal mail

From: Dave Crocker <[email-masked]>
Date: Thu, 16 Dec 2021 11:18:53 -0800

When postal mail iis 'delivered', it is dropped at the destination.  
What is done to it after that is /after/ delivery. Someone at the 
destination might look at the envelope and decide to give it to a 
different house member.  They might decide to forward it, unopened, to 
someone else.  But again, from the perspective of the postal handling 
service, this is after delivery.

Registered mail even documents this point.

If someone is going to claim that the Post Office did not actually 
deliver the mail and, for example, it is not 'delivered' until it is 
placed into the recipient's mailbox -- as opposed to the household 
mailbox -- they need to explain this carefully.

It will then be quite helpful for them to explain why and how Internet 
Mail justifies a different model.

d/

-- 
Dave Crocker
Brandenburg InternetWorking
bbiw.net

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From: "John Levine" <[email-masked]>
Date: 16 Dec 2021 15:09:03 -0500

>Mail justifies a different model.

If I have filed a forwarding order with the PO, they slap a yellow sticker
on mail addressed to me and send it to the new addreess, all within the
postal system, without it ever touching the original mailbox.

I can report that a fair amount of local aliasing happens within the PO.
For example, my local post office moved to a new building and they had to change
some of the PO box numbers, including mine.  Nonetheless, if someone sends mail
to the old box, it goes into my new box.  Also, I get a daily newspaper addressed
to my house, but if the paper arrives after the carrier has left, they usually put
it in my box so I can get it the same day.

I was under the impression that people stopped saying that paper mail was the
model for e-mail around 1980, but if not, I'm glad to see that we agree
that forwarding and local aliasing are an integral part of the service.

R's,
John

---

From: Dave Crocker <[email-masked]>
Date: Thu, 16 Dec 2021 12:15:17 -0800

> postal system, without it ever touching the original mailbox.

Ahh.  So you do see aliasing as an MTA function.  Interesting.

A problem with that is that forwarding order, with them, is part of the 
independent transfer service, whereas the reality in email is that it is 
a function at the recipient destination.  Not the last hop before the 
recipient's address, as with the post office, but actually /at/ the 
recipient address.

Quite a different ball of formal and administrative responsibility.

> that forwarding and local aliasing are an integral part of the service.

Interesting claim.  I don't recall it being true then or since.  Perhaps 
you can document your view.  Failing that, perhaps you can explain how 
your reference is relevant to the point I was/am seeking to make about 
architectural distinctions?

d/

---

From: "John Levine" <[email-masked]>
Date: 16 Dec 2021 15:57:20 -0500

It appears that Dave Crocker  <[email-masked]> said:
>independent transfer service,

Sorry, but I have no idea what you mean by "independent transfer service" and I
don't think I want to know.

Among the many reasons that postal mail is not a useful model for e-mail is
that postal mail is run by a small set of organizations with formal relationships
based on contract and treaty, while e-mail is a large set of organizations with
no relation at all, just shared software protocols.

As I'm sure you remember, attempts like Goodmail to overlay a contract scheme
on top of e-mail have all been failures.

Barring some persuasive argument that we've been wrong for 40 years about the
irrelevance of postal mail, I don't plan to argue about this any more.

R's,
John

---

From: John C Klensin <[email-masked]>
Date: Thu, 16 Dec 2021 16:07:02 -0500

--On Thursday, December 16, 2021 12:15 -0800 Dave Crocker
<[email-masked]> wrote:

>>> It will then be quite helpful for them to explain why and
>>> how Internet Mail justifies a different model.
>> 
>> If I have filed a forwarding order with the PO, they slap a
>> yellow sticker on mail addressed to me and send it to the new
>> addreess, all within the postal system, without it ever
>> touching the original mailbox.
> 
> A problem with that is that forwarding order, with them, is
> part of the independent transfer service, whereas the reality
> in email is that it is a function at the recipient
> destination.  Not the last hop before the recipient's address,
> as with the post office, but actually /at/ the recipient
> address.

Dave,

I may just not understand the distinction you are trying to make
but, if I were to move to California next week and file a change
of address notification with the postal service, and you then
sent mail to me, that letter would get all the way across the
country to New England, to one of two regional sorting
facilities, before being rerouted to California.  Whether it
would get to my local post office (about three blocks away), to
the facility at which letters are sorted into bags for handling
by carriers (about a mile away), or one of the regional
facilities or some subsidiary of it, might depend on which of my
Cambridge addresses you sent it to, exactly how the mail piece
was addressed, and whether the mail piece was handled as a
letter or a small parcel.  It also might depend on the time of
year.  If, instead of sending a message to me, you sent it to
the New Hampshire address of a colleague who recently moved to
the West Coast, most of the above would be different, not just
because of the difference in states/ locations but because his
address was part of a rural delivery service rather than the
conventional more urban ones (and you couldn't tell his was
rural delivery by looking at the address although sometimes you
still can).

All of those choices about routing and where the change of
address would be noticed, the sticker affixed, and rerouting
would occur would be out of both your control as sender and mine
(or my colleague's) as the ultimate recipient. 

Different countries might do things differently.  Or not.

I don't see that as significantly different from what we do with
Internet mail.  The analogy gets even stronger if someone is
using an email address of the form [email-masked] at a company
but that address is rewritten to a location-dependent one, e.g.,
[email-masked] by some process associated with the
servers for example.com.  And, if that user changes locations,
how soon incoming messages will be rewritten to, e.g.,
[email-masked] by that central management system or
whether they will go to Seattle for a while and be
rewritten/forwarded there (and where messages will be rejected
if that user leaves the company entirely) will differ from
company to company with the one thing in common being that the
envelope is never opened and, with the exception of trace
fields, the headers are never opened or affected.   

We make some of that work within our models by handwaving about
"ADMD"s -- a concept that, as you know, came from X.400 and was
not part of our vocabulary when 821/822 were written -- but,
again, I see little if any significant difference from the
postal model.

> Quite a different ball of formal and administrative

I don't see the distinction you are trying to make as clear,
much less important to what we should do with 5321bis/5322bis.

>...

best,
   john

---

From: Dave Crocker <[email-masked]>
Date: Thu, 16 Dec 2021 14:58:19 -0800

> don't think I want to know.

Seems to be a pattern.

And yet the distinction between 'part of the transit' versus 'part of 
the source' (originating) or 'part of the destination' (receiving) 
matter quite a bit here.  The nature of their responsibilities and 
authorizations vary enormously.

> no relation at all, just shared software protocols.

All of that is very nice, but doesn't attend to the specifics, here, 
absent your created specific linkages.

> on top of e-mail have all been failures.

Goodmail had nothing to do with independent transfer services, like 
postal mail.  It had to do with independent reputation certification of 
the author.  Quite a different thing.  And for all intents and purposes, 
none of the email reputation startups succeeded, no matter the model 
they offered.

So this is another reference that turns out to be irrelevant to the 
current case.

> irrelevance of postal mail, I don't plan to argue about this any more.

Excellent.  Does that mean you'll try to respond to the substance, instead?

d/

---

From: Martin J. Dürst <[email-masked]>
Date: Fri, 17 Dec 2021 09:01:07 +0900

Reading the thread with quite some interest, it seems as if Dave is 
equating organizations that handle email (like example.com) to 
households in the postal system, but John K. (and probably John L.) is 
equating them to independent postal systems.

Given that an SMTP connection (e.g. between a.foo.com and b.bar.org) is 
essentially just a handover (such as it may happen in the postal system 
between countries, or between different sub-units of a country's postal 
system) and not a system in and by itself, John's view seems more 
appropriate to me. The email system would then have (way) more 
independent "postal services" than the snail mail system. That is unless 
we count organizations and households as independent systems, which at 
least in the case of companies with their internal mail-handling 
infrastructure may well be justified.

Also, Dave gave registered mail as an example. In the postal system, 
receipt of registered mail is confirmed at the household door. I (and in 
my I guess most email users) have little practical experience with Mail 
Disposition Notifications (RFC 8098). However, the choices there 
(displayed/deleted/dispatched/processed) suggest that an MDN from a 
recipient after forwarding/aliasing is at least an option, and probably 
the most desirable one. This would put delivery at that point.

Anyway, all that's assuming the analogies help.

I think the IETF way as I know it would be to go back to actual protocol 
consequences (architecture is just hot air if it doesn't change what's 
happening "on the ground"), and to actual proposals for textual changes.

Regards,   Martin.

-- 
Prof. Dr.sc. Martin J. Dürst
Department of Intelligent Information Technology
College of Science and Engineering
Aoyama Gakuin University
Fuchinobe 5-1-10, Chuo-ku, Sagamihara
252-5258 Japan

---

From: Dave Crocker <[email-masked]>
Date: Fri, 17 Dec 2021 15:04:38 -0800

Hi Martin,

> equating them to independent postal systems.

More specifically, my point is that:

    1. The end system is a distinct authority from the handling systems 
earlier in the transit sequence.

    2. Internet mail specifications distinguish between who is expected 
to treat the LHS string as opaque and who is expected to process it -- 
except perhaps for some error conditions -- where that last system in 
the sequence is the only one to do LHS process and is identified in the 
RHS domain name.

    3. Aliases and mailing list managers reside within the authority of 
that last system.

The postal model I offered matches all these details.

The one John offered does not.

Instead he offered one that I believe has no equivalent in Internet Mail 
specifications.  That it might occur in the wild is nice but irrelevant, 
since we are talking about our specs, not the full range of what happens 
in the wild.

John's model essentially puts aliasing in the MTA.  Mine does not.  (We 
can debate whether it is in the MDA vs. a post-delivery, user-level 
process, as a separate matter.)

> appropriate to me. 

Please reconsider a bit further, given my above points.

> The email system would then have (way) more 
> independent "postal services" than the snail mail system. 

It does.  But how does that matter, for this topic?

> That is unless 

Exactly.  Because in the Internet Mail model, they are indeed 
independent services.

(RFC 5598, invokes the ADMD term to emphasize this essential point.

> receipt of registered mail is confirmed at the household door.

I cited Registered mail because it documents the steps.  However general 
the semantics apply to all postal mail.

The post office delivers to a physical address, not to person.  I am 
still getting mail for my house's previous owner, from 35 years ago. 
(The mechanism John cited is exceptional.)  Email is handed to the RHS 
domain name's handling service, without regard to the LHS value.

John's example was for something that happens before that.  But aliasing 
and mailing lists happen after it.  As does the Postal example I cited.

When the post office transfers the mail to the household, it is 
considered delivered.

If someone in the household does something other than get it to the 
person named in the first line, that is /after/ 'initial' delivery and 
IMO it is quite reasonable to call completion of that re-routing a 
second delivery.

 >    I (and in> my I guess most email users) have little practical 
experience with Mail
> the most desirable one. This would put delivery at that point.

MDN is a user-level process, not a handling/transfer service process. 
The difference is fundamental.

And the difference in their names is relevant:  DSN (RFC 3464) refers to 
delivery, and is part of the infrastructure effort.  MDN (RFC 8098) 
refers to disposition.

Note RFC 8098's second sentence in its first paragraph:

   "An MDN can be used to notify the sender of a
    message of any of several conditions that may occur after successful
    delivery, such as display of the message contents, printing of the
    message, deletion (without display) of the message, or the
    recipient's refusal to provide MDNs."

Use of the word 'after' is key.

The RFC's Section 4 (Timeline of Events) is also especially enlightening.

RFC 3464 cites 'delivery':

   '"delivered" indicates that the message was successfully delivered to
                the recipient address specified by the sender, which
                includes "delivery" to a mailing list exploder.'

And as much as some folk want to claim a major difference between 
aliases and mailing lists, please note the language in this other DSN 
action-value:

    '"expanded"  indicates that the message has been successfully
                delivered to the recipient address as specified by the
                sender, and forwarded by the Reporting-MTA beyond that
                destination to multiple additional recipient addresses.
                An action-value of "expanded" differs from "delivered" in
                that "expanded" is not a terminal state.'

(There is more to consider in that text, and I hope that discussion here 
can progress with enough substance to engage on its finer points.)

> happening "on the ground"), and to actual proposals for textual changes.

Agreed.

d/