Re: [ietf-smtp] Stray <LF> in the middle of messages

John C Klensin <john-ietf@jck.com> Sat, 06 June 2020 20:03 UTC

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Date: Sat, 06 Jun 2020 16:03:40 -0400
From: John C Klensin <john-ietf@jck.com>
To: Paul Smith <paul@pscs.co.uk>
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Subject: Re: [ietf-smtp] Stray <LF> in the middle of messages
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--On Saturday, June 6, 2020 19:36 +0100 Paul Smith
<paul@pscs.co.uk> wrote:

>... 
> I suppose with a submission server you could be more flexible,
> but, to be honest, I've *never* come across a case where not
> treating a lone LF as a line break has been a problem.
>...

And that is exactly why the last sentence of the introductory
paragraph of Section 8 of RFC 4409 says:

	"Any message forwarded or delivered by the MSA MUST
	conform to the requirements of [SMTP-MTA] and
	[MESSAGE-FORMAT]."

In other words, perfectly reasonable for a submission server to
reach a local agreement that bare LFs are to be treated as line
terminators but, by the time the message reaches the public
Internet, it needs to have fixed those.

    john