Re: [ietf-smtp] on liberality, was MTS-STS_validation

Dave Crocker <dhc@dcrocker.net> Sun, 04 April 2021 21:17 UTC

Return-Path: <dhc@dcrocker.net>
X-Original-To: ietf-smtp@ietfa.amsl.com
Delivered-To: ietf-smtp@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id E55D23A1AB8 for <ietf-smtp@ietfa.amsl.com>; Sun, 4 Apr 2021 14:17:40 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -2.1
X-Spam-Level:
X-Spam-Status: No, score=-2.1 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_BLOCKED=0.001, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001] autolearn=ham autolearn_force=no
Authentication-Results: ietfa.amsl.com (amavisd-new); dkim=pass (2048-bit key) header.d=dcrocker.net
Received: from mail.ietf.org ([4.31.198.44]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id JnBXa1IcNQcc for <ietf-smtp@ietfa.amsl.com>; Sun, 4 Apr 2021 14:17:36 -0700 (PDT)
Received: from quail.birch.relay.mailchannels.net (quail.birch.relay.mailchannels.net [23.83.209.151]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 105FB3A1AB7 for <ietf-smtp@ietf.org>; Sun, 4 Apr 2021 14:17:35 -0700 (PDT)
X-Sender-Id: hostingeremail|x-authsender|dhc@dcrocker.net
Received: from relay.mailchannels.net (localhost [127.0.0.1]) by relay.mailchannels.net (Postfix) with ESMTP id 1CCA17024A2 for <ietf-smtp@ietf.org>; Sun, 4 Apr 2021 21:17:35 +0000 (UTC)
Received: from nl-srv-smtpout2.hostinger.io (100-96-27-144.trex.outbound.svc.cluster.local [100.96.27.144]) (Authenticated sender: hostingeremail) by relay.mailchannels.net (Postfix) with ESMTPA id 3CE1E701C6A for <ietf-smtp@ietf.org>; Sun, 4 Apr 2021 21:17:32 +0000 (UTC)
X-Sender-Id: hostingeremail|x-authsender|dhc@dcrocker.net
Received: from nl-srv-smtpout2.hostinger.io ([UNAVAILABLE]. [145.14.159.14]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256) by 100.96.27.144 (trex/6.1.1); Sun, 04 Apr 2021 21:17:34 +0000
X-MC-Relay: Neutral
X-MailChannels-SenderId: hostingeremail|x-authsender|dhc@dcrocker.net
X-MailChannels-Auth-Id: hostingeremail
X-Quick-Spill: 583ec79f2e2cbc25_1617571054782_3959798245
X-MC-Loop-Signature: 1617571054782:2999116950
X-MC-Ingress-Time: 1617571054781
Received: from [192.168.0.109] (108-226-162-63.lightspeed.sntcca.sbcglobal.net [108.226.162.63]) (Authenticated sender: dhc@dcrocker.net) by nl-srv-smtpout2.hostinger.io (smtp.hostinger.com) with ESMTPSA id 54FE2333EFB7 for <ietf-smtp@ietf.org>; Sun, 4 Apr 2021 21:17:30 +0000 (UTC)
DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=dcrocker.net; s=hostingermail-a; t=1617571050; bh=NkKwUdA9I4QS4mszpJjgIUmRc+G6inaqJFlhplvHI1w=; h=Reply-To:Subject:To:References:From:Date:In-Reply-To; b=dmjHSO/orEvmeIlVhSKaop6xcUg9Z5Fy4WPuX/g7xdcHnKS8+aHrePv1cNSn/Adei j/MPBItbCcuKBIwdJ0rSx5FEV8MisuGU5bonKSVHIx5kAypS3m5WzlxxPtvCPg0SO8 9CGhu8DB8hlSGtUB16ruqvouZQOouMVEUrQa6uqVIkod+YzDJyJ0l4sK/w+cNvU3dn P3taUl9WeBxzLUBfs4gNaKZLl58ju5GEnfyrPW57WyvpBJZCaYbt1p5tWjZ2ldCizK CAOBR4LzE/s9uPbKCKQKKRHDlFZ2DyumH8XD1jTyUntDmdlICKZ7o1tVChBCa+WoMw oyofJQnZkP0Ug==
Reply-To: dcrocker@bbiw.net
To: ietf-smtp@ietf.org
References: <20210404211320.5302671FB8BC@ary.qy>
From: Dave Crocker <dhc@dcrocker.net>
Organization: Brandenburg InternetWorking
Message-ID: <e1b1d3db-7207-2486-1631-6669a9eb22e2@dcrocker.net>
Date: Sun, 4 Apr 2021 14:17:28 -0700
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.9.0
MIME-Version: 1.0
In-Reply-To: <20210404211320.5302671FB8BC@ary.qy>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Archived-At: <https://mailarchive.ietf.org/arch/msg/ietf-smtp/sLaxZcLpbxQiHR5hGqKIcBVZyZE>
Subject: Re: [ietf-smtp] on liberality, was MTS-STS_validation
X-BeenThere: ietf-smtp@ietf.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: "Discussion of issues related to Simple Mail Transfer Protocol \(SMTP\) \[RFC 821, RFC 2821, RFC 5321\]" <ietf-smtp.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/ietf-smtp>, <mailto:ietf-smtp-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/ietf-smtp/>
List-Post: <mailto:ietf-smtp@ietf.org>
List-Help: <mailto:ietf-smtp-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/ietf-smtp>, <mailto:ietf-smtp-request@ietf.org?subject=subscribe>
X-List-Received-Date: Sun, 04 Apr 2021 21:17:41 -0000

On 4/4/2021 2:13 PM, John Levine wrote:
> One could read the standard either way,

The above is an example of the essential requirement to Postel's 
directive.  In the face of possible ambiguity in how a standard is 
interpreted, try to be conservative in what you send and try to be 
liberal in what you accept.

Absent that kind of contextual constraint, the directive produces 
non-interoperability.

d/

-- 
Dave Crocker
Brandenburg InternetWorking
bbiw.net