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

Ned Freed <ned.freed@mrochek.com> Mon, 15 March 2021 16:23 UTC

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Cc: Ned Freed <ned.freed@mrochek.com>, ietf-smtp@ietf.org
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Date: Mon, 15 Mar 2021 08:58:06 -0700 (PDT)
From: Ned Freed <ned.freed@mrochek.com>
In-reply-to: "Your message dated Mon, 15 Mar 2021 08:30:02 -0700" <e6e5d166-ded5-b6c0-db9a-57c44e8bd92a@dcrocker.net>
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To: Dave Crocker <dhc@dcrocker.net>
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Subject: Re: [ietf-smtp] [Emailcore] Proposed ESMTP keyword RCPTLIMIT
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> On 3/15/2021 7:59 AM, Ned Freed wrote:
> > 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 for doing this.

No sweat.

> Quick comments:

> In the Introduction, I suggest adding:

>       SMTP servers have always been able to announce a limit, in a
> reply, which means that the client first needed to issue a command.  The
> mechanism specified here avoids the overhead of that interactions, by
> announcing limits prior to any substantive interaction.

Nice. Added.

> Also:

>       The Limits mechanism provides an announcement at the start of a
> session.  Some servers vary their limits, as a session progresses, based
> on their obtaining more information.  The Limits mechanism does not
> cover in-session limitation changes.

This was on the to-do list, but I was struggling with the language. This helps.

However, I did have another idea here: It would be possible for a server to
indicate that a limit change has occured through the use of a special enhanced
status code - probably limited to ones on successful repsonses. This would
instruct the client to reissue EHLO at the next opportunity to obtain updated
limits.

I think this is overengineered and opted not to include it, but I'd like
feedback from others on the point.

				Ned