Re: [ietf-smtp] homework, not an experiment, draft-crocker-email-deliver

Dave Crocker writes:

> >    "Delivered-To:" FWS Mailbox CRLF
> >                     ; Mailbox is from [SMTP]
>
> I don't see anything in either that prohibits what you've described.
The sticking point is "Mailbox is from [SMTP]" is getting interpreted to  
mean "literally what's in the RCPT TO'.
This is not always the case. Example: mail received by a mailing list  
server, and then delivered to a local mailbox (that's subscribed to the  
mailing list), will have two Delivered-To: headers. The first one will be  
the mailing list's public SMTP address (or may be not, but it will be  
something(_at_)example(_dot_)com where "something" is how example.com's mail server  
knows the mailing list's mailbox by), the second one will be the recipient's  
address, which may or may not be a public SMTP address (for the same  
reasons).
Another live example, using my isolated network, but with a couple of  
servers that occasionally swap SMTP mail:
$ telnet localhost 25
Trying ::1...
Connected to localhost.
Escape character is '^]'.
220 monster.email-scan.com ESMTP
EHLO monster.email-scan.com
250-monster.email-scan.com Ok.
250-AUTH CRAM-SHA256 CRAM-SHA1 CRAM-MD5
250-STARTTLS
250-XVERP=Courier
250-XEXDATA
250-XSECURITY=NONE,STARTTLS
250-PIPELINING
250-8BITMIME
250-SMTPUTF8
250-SIZE
250 DSN
MAIL FROM:<postmaster(_at_)monster(_dot_)email-scan(_dot_)com>
250 Ok.
RCPT TO:<postmaster(_at_)monster(_dot_)email-scan(_dot_)com>
250 Ok.
DATA
354 Ok.
Subject: test
From: postmaster(_at_)monster(_dot_)email-scan(_dot_)com
To: postmaster(_at_)monster(_dot_)email-scan(_dot_)com
Subject: local mail

test
.
250 Ok. 00000000610B21CB.00014A01
QUIT
221 Bye.
Connection closed by foreign host.

Would anyone care how the headers would look like?

Delivered-To: mrsam(_dot_)virtual(_at_)monster(_dot_)email-scan(_dot_)com
Return-Path: <postmaster(_at_)monster(_dot_)email-scan(_dot_)com>
Received: from monster.email-scan.com (localhost [::1])
 by monster.email-scan.com with ESMTP
 id 0000000000068359.00000000610B21CB.00014A01; Wed, 04 Aug 2021 19:24:44 -0400
Subject: test
From: postmaster(_at_)monster(_dot_)email-scan(_dot_)com
To: postmaster(_at_)monster(_dot_)email-scan(_dot_)com
Subject: local mail

test

The Delivered-To: header has nothing to do with the SMTP recipient. This  
node owns @monster.email-scan.com, and it's up to this node to decide what  
goes in there.

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