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

Richard Clayton <> Tue, 20 April 2021 15:55 UTC

Return-Path: <>
Received: from localhost (localhost []) by (Postfix) with ESMTP id 80DF13A2908 for <>; Tue, 20 Apr 2021 08:55:12 -0700 (PDT)
X-Virus-Scanned: amavisd-new at
X-Spam-Flag: NO
X-Spam-Score: -1.899
X-Spam-Status: No, score=-1.899 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001] autolearn=ham autolearn_force=no
Received: from ([]) by localhost ( []) (amavisd-new, port 10024) with ESMTP id cqg2mPNYANWK for <>; Tue, 20 Apr 2021 08:55:08 -0700 (PDT)
Received: from ( []) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by (Postfix) with ESMTPS id EABBE3A2904 for <>; Tue, 20 Apr 2021 08:55:07 -0700 (PDT)
Received: from localhost ([]:36177 by with esmtp (Exim 4.94) (envelope-from <>) id 1lYsiM-0009G5-So; Tue, 20 Apr 2021 15:55:02 +0000
Message-ID: <>
Date: Tue, 20 Apr 2021 16:53:45 +0100
To: Ned Freed <>
From: Richard Clayton <>
References: <> <20210315234648.563C0708B340@ary.qy> <> <> <> <> <> <> <>
In-Reply-To: <>
MIME-Version: 1.0
X-Mailer: Turnpike Integrated Version 5.03 M <nz0$+bQP77vdGOKLYuS+dOCCip>
Archived-At: <>
Subject: Re: [ietf-smtp] [Emailcore] Proposed ESMTP keyword RCPTLIMIT
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: "Discussion of issues related to Simple Mail Transfer Protocol \(SMTP\) \[RFC 821, RFC 2821, RFC 5321\]" <>
List-Unsubscribe: <>, <>
List-Archive: <>
List-Post: <>
List-Help: <>
List-Subscribe: <>, <>
X-List-Received-Date: Tue, 20 Apr 2021 15:55:12 -0000

In message <>om>, Ned Freed
<> writes

>> as I observed before -- don't expect much more than a generic statement
>> (which comes down to "sending N good emails is the most you can expect
>> to be able to manage") from such systems. Anything which revealed the
>> current view ("actually, you've pretty much exhausted our patience")
>> just is not going to happen (IMO)
>I don't really understand the concern here, 

Some bad senders start by sending good email and then, once their
reputation is established, send bad email. It is generally thought to be
unwise to give any clues whatsoever as to how well this process might be
going... (to what extent the machine learning system has been fooled)

>and more importantly, how to address

It is inherent that you cannot -- so mailbox providers who operate in
the space where this is a significant issue are not going to provide any
fine-grained data whatsoever -- just generic values.

I take Laura's point that good senders can deduce the upper limits --
and hence providing data about those upper limits at the start of the
session has a small amount of value (if only in ensuring that sessions
close smoothly and fewer exception logging event are generated)

richard                                                   Richard Clayton

Those who would give up essential Liberty, to purchase a little temporary 
Safety, deserve neither Liberty nor Safety. Benjamin Franklin 11 Nov 1755