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

2021-03-15 11:32:46
On Mar 15, 2021, at 12:59 PM, Ned Freed 
<ned(_dot_)freed(_at_)mrochek(_dot_)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 
beginnings of a specification:

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 ;-)


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