Re: [ietf-smtp] [Emailcore] Proposed ESMTP keyword RCPTLIMIT

Ned Freed <ned.freed@mrochek.com> Mon, 15 March 2021 16:32 UTC

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Date: Mon, 15 Mar 2021 09:19:44 -0700 (PDT)
From: Ned Freed <ned.freed@mrochek.com>
In-reply-to: "Your message dated Mon, 15 Mar 2021 14:12:05 -0200" <7223914D-87EA-46E1-91BF-72EB333FCA61@dukhovni.org>
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To: Viktor Dukhovni <ietf-dane@dukhovni.org>
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Subject: Re: [ietf-smtp] [Emailcore] Proposed ESMTP keyword RCPTLIMIT
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> > On Mar 15, 2021, at 12:59 PM, Ned Freed <ned.freed@mrochek.com> wrote:
> >
> > The idea of a limits extension has come up several times before, but
> > for various reasons never went forward.
> >
> > I think this extension is an important thing to have, so I've put together the
> > beginnings of a specification:
> >
> > https://datatracker.ietf.org/doc/draft-freed-smtp-limits/

> Thanks.  I noted that parameters for the "LIMITS" keywork are ";" delimited,
> that's not the common pattern in EHLO keywords, where e.g. SASL mechanisms,
> are space-separated.

(I was wondering if anyone would notice this.)

It may be a common pattern - and in fact it's what I used initially. But then I
checked, and it's actually syntactically invalid according to RFC 5321:

   ehlo-line      = ehlo-keyword *( SP ehlo-param )

   ehlo-keyword   = (ALPHA / DIGIT) *(ALPHA / DIGIT / "-")
                    ; additional syntax of ehlo-params depends on
                    ; ehlo-keyword

   ehlo-param     = 1*(%d33-126)
                    ; any CHAR excluding <SP> and all
                    ; control characters (US-ASCII 0-31 and 127
                    ; inclusive)

I couldn't believe this was how it was originally specified, but sure enough,
it's what RFC 1869 says as well.

I'm now pondering what to do about my XCLIENT implementation...

> It seems unlikely that limits will be anything but
> boolean or numeric, and so ";" looks a bit out of place to me.

I could imagine a comma-separated value list. Maybe.

> It feels more like MIME rather than SMTP. :-) :-)

It seemed like a reasonable fallback syntax ;-)

				Ned