Re: [ietf-smtp] [Proposal] 250-MARKDOWN

[[e-mail]]

On Wed, 09 Jan 2019 09:20:34 +0100, Gilles Chehade said:

> well, as someone writing a server implementation:
>
>       When a server says that "I recognize markdown format"
>
> that sentence doesn't make sense to me because the server does not recognize a
> format or another, it's in charge of the transport, not of rendering or making
> any sense out of the DATA part. it feels like a violation of layer, DATA spill
> over transport.

And you're totally correct - it *is* a layering violation.  For ages, there's
been a *very* strict separation between the SMTP transport layer and the
RFC822/MIME in the DATA portion. The only extension listed in the below EHLO
that isn't *strictly* SMTP is '8bitmime' - and *that* only gets included
because there is a documented non-lossy and invertable way to convert from
'Content-Transfer-Encoding: 8bit' down to 7bit if a non-8bit-clean path is
encountered.

Consider that the following SMTP transaction is actually *legal* and accepted
by Sendmail:

[~] telnet ::1 25
Trying ::1...
Connected to ::1.
Escape character is '^]'.
220 turing-police.cc.vt.edu ESMTP Sendmail 8.15.2/8.15.2; Wed, 9 Jan 2019 04:26:52 -0500
EHLO localhost
250-turing-police.cc.vt.edu Hello turing-police.cc.vt.edu [IPv6:0:0:0:0:0:0:0:1], pleased to meet you
250-ENHANCEDSTATUSCODES
250-PIPELINING
250-8BITMIME
250-SIZE
250-DSN
250-ETRN
250-AUTH GSSAPI DIGEST-MD5 CRAM-MD5
250-DELIVERBY
250 HELP
MAIL FROM:<>
250 2.1.0 <>... Sender ok
RCPT TO:<valdis@localhost>
250 2.1.5 <valdis@localhost>... Recipient ok
DATA
354 Enter mail, end with "." on a line by itself
There are exactly zero RFC822 headers in this DATA package.
.
250 2.0.0 x099QqgX005006 Message accepted for delivery
QUIT
221 2.0.0 turing-police.cc.vt.edu closing connection

And Sendmail Does The Right Thing - takes the whole thing, even lacking rfc822
headers (which it doesn't need for delivery because the RCPT TO told it
everything it needed to know).  It fixes up Date: and Message-id: (possibly
debatable for port 25), adds the required Received: and Return-Path: headers,
and hands the whole thing to procmail, which stashes it into an nmh file in my
inbox folder.

[~] scan +inbox last:3
 65122  *    M 12:54 +00     19k IBM Announcement   IBM United States Announcement Letters
 65131  *   *  18:15 +01      4k Matthias Waehlisc  Re: BGP Experiment <<It's well-known: A fork of Quagga. Cheers matth
 65141 U     ? 04:26 -05      0k To:                 <<There are exactly zero RFC822 headers in this DATA package. 
[~] cat Mail/inbox/65141
Return-Path: <[e-mail]>
Received: from localhost (turing-police.cc.vt.edu [IPv6:0:0:0:0:0:0:0:1]) 	by turing-police.cc.vt.edu (8.15.2/8.15.2) with ESMTP id x099QqgX005006 	for <valdis@localhost>; Wed, 9 Jan 2019 04:27:15 -0500
Date: Wed, 9 Jan 2019 04:26:52 -0500
Message-Id: <[e-mail]>

There are exactly zero RFC822 headers in this DATA package.