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

Dave Crocker <> Mon, 15 March 2021 15:30 UTC

Return-Path: <>
Received: from localhost (localhost []) by (Postfix) with ESMTP id 00CEB3A14AC for <>; Mon, 15 Mar 2021 08:30:19 -0700 (PDT)
X-Virus-Scanned: amavisd-new at
X-Spam-Flag: NO
X-Spam-Score: -1.234
X-Spam-Status: No, score=-1.234 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_BLOCKED=0.001, SPF_SOFTFAIL=0.665, URIBL_BLOCKED=0.001] autolearn=no autolearn_force=no
Authentication-Results: (amavisd-new); dkim=pass (2048-bit key)
Received: from ([]) by localhost ( []) (amavisd-new, port 10024) with ESMTP id gaZWJ4BMKx9L for <>; Mon, 15 Mar 2021 08:30:17 -0700 (PDT)
Received: from ( []) (using TLSv1.2 with cipher ADH-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by (Postfix) with ESMTPS id BDF643A1509 for <>; Mon, 15 Mar 2021 08:30:08 -0700 (PDT)
Received: from compute1.internal (compute1.nyi.internal []) by mailforward.nyi.internal (Postfix) with ESMTP id 019E119419E8; Mon, 15 Mar 2021 11:30:08 -0400 (EDT)
Received: from mailfrontend1 ([]) by compute1.internal (MEProxy); Mon, 15 Mar 2021 11:30:08 -0400
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=; h=content-transfer-encoding:content-type :date:from:in-reply-to:message-id:mime-version:references :reply-to:subject:to:x-me-proxy:x-me-proxy:x-me-sender :x-me-sender:x-sasl-enc; s=fm2; bh=CNBxbo/zH6kCDge/ATXUNJwyleIQk wdKhesugOHSRN8=; b=cJE/jXvt0O9odxhUNjhDaNuW54L3Dq9n8RgY5lp7ybmHr c0eDEJ6JcQfGnkRzLaY8yFswKqAAVxdas850biZFbZmu6okgJIkfg7fIBsVsd/GM eYkzKhDas+nKQcK0N7wqMWPuwQvVdPkYGDbKdyiOCdl1tvC2nda8jWvE4coKKou3 rW7A22Yg/8MahPK1D6GRZsC8jkGq7bwdh55n1xl3EcefZ0U5qIWk992ziPXytV28 6WGOs3ylXCKIBNC/9nNlH1nWS9l8Xi3/C1/T0uDyBm0ODpEDJiImpiqDiTtBP8zh r+FDylV1MX1GziWNYGQZQFyNoOvznzbZA+9pqxLMA==
X-ME-Sender: <xms:fn1PYPGhdQvT_UVnam_cZz-OuSz7DKw0Dye251ODVxrVjOzLZP0n0w> <xme:fn1PYMT6NUFVFG4ndkIhi62el9p1lY9vOQyjzVCV8KGnk1q8ZYUyRZqoHdPXHEYR7 2OnEmuwViFZN5RaVw>
X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgeduledruddvledgjeejucetufdoteggodetrfdotf fvucfrrhhofhhilhgvmecuhfgrshhtofgrihhlpdfqfgfvpdfurfetoffkrfgpnffqhgen uceurghilhhouhhtmecufedttdenucesvcftvggtihhpihgvnhhtshculddquddttddmne cujfgurheprhfuvfhfhfhokffffgggjggtgfesthejredttdefjeenucfhrhhomhepffgr vhgvucevrhhotghkvghruceoughhtgesuggtrhhotghkvghrrdhnvghtqeenucggtffrrg htthgvrhhnpeffheehteetueejfeektedtkeelkeefudelteevueekudejueegleevvdet teehgeenucffohhmrghinhepihgvthhfrdhorhhgpdgssghifidrnhgvthenucfkphepud dtkedrvddviedrudeivddrieefnecuvehluhhsthgvrhfuihiivgeptdenucfrrghrrghm pehmrghilhhfrhhomhepughhtgesuggtrhhotghkvghrrdhnvght
X-ME-Proxy: <xmx:fn1PYODSHAmHfw6dEhK0v0JsS429UzoJ4k753QlSoCJnlWcGVFUqkg> <xmx:fn1PYE325S5rnWG08DFcUwmVUZN1FiymCMGjfjokeXDMxX3fRin2qg> <xmx:fn1PYEUWLnf7fAxNfBfXHdSSMNCG9GMAE_obVi2UmR4aaZxVmzpEsg> <xmx:f31PYM9voumDEMhsmQK6trHt6Yl_R_IXvg2fQnbH4vbYm5PRf-EcPA>
Received: from [] ( []) by (Postfix) with ESMTPA id E07E1240072; Mon, 15 Mar 2021 11:30:05 -0400 (EDT)
To: Ned Freed <>,
References: <> <20210312203224.F3739701E4C5@ary.qy> <>
From: Dave Crocker <>
Organization: Brandenburg InternetWorking
Message-ID: <>
Date: Mon, 15 Mar 2021 08:30:02 -0700
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1
MIME-Version: 1.0
In-Reply-To: <>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Language: en-US
Content-Transfer-Encoding: 7bit
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: Mon, 15 Mar 2021 15:30:24 -0000

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:

Thanks for doing this.

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.


      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.

Dave Crocker
Brandenburg InternetWorking