entêtes ARC sur configuration avec SPF, DKIM et DMARC en place.

Bonjour,

Ne confondez pas:

SPF, DKIM et DMARC c'est pour authentifier vos mails sortants

L'ajout d'enregistrements ARC se fait au niveau d'un serveur en réception, lorsqu'il forwarde un mail via une redirection. 

Je peux vous dire que pour un mail reçu ce matin depuis un site américain et via une redirection OVH, il y a bien des enregistrements ARC qui ont été ajoutés par OVH lors de la redirection. J'ignore si tous les clusters OVH  et toutes les plateformes font de même. En particulier j'ai un sérieux doute concernant les redirections que vous configurez via OutlookWeb, qui casse même DKIM dans la plupart des cas.

Voici un extrait des en-têtes de ce message entre groups.io (émetteur) et dmmail.eu (récepteur) via le mutualisé OVH.

Authentication-Results: k3.dmmail.eu;
	dkim=pass (2048-bit key; unprotected) header.d=groups.io header.i=@groups.io header.a=rsa-sha256 header.s=groups1 header.b=LMSWqwOL;
	dkim-atps=neutral
Received: from 2.mo615.mail-out.ovh.net (2.mo615.mail-out.ovh.net [87.98.181.235])
	by k3.dmmail.eu (Postfix) with ESMTPS id 212CCFF7E0
	for <*@*.net>; Wed,  1 Oct 2025 07:37:56 +0000 (UTC)

Received: from [10.42.3.30] (unknown [10.110.118.5])
	by mo615.mail-out.ovh.net (Postfix) with ESMTPS id 4cc6GX4L2sz5wdh
	for <*@*.net>; Wed,  1 Oct 2025 07:37:56 +0000 (UTC)
ARC-Seal: i=1; a=rsa-sha256; cv=none; d=mail.ovh.net; s=arc-20240129-1;
    t=1759304276; b=MGRkiLfpbnh1kMW0+tyWhrik+m3XEyUHu2i/GqvknDdKIia
    bq6e5UdGmYUm/oJ5JrgNRDoWWgSOPpMpLZdL5RJHMImQW6PAJZ7lLz5v6/1cZWo2
    PqhrgG4BoMecywuRUJSBpgKyKYzPqMPbgP9JuWwW7g9cXW+9eUt5QttuJ0s6/paz
    SAz8Kw3RYGPhUQuwMQ9e8iHWQZYTpYs9dMj9FCGx/B1fk6JeZ41OoNurW5FqTS2K
    PlvYKl5nNBzL15Gchn8koydn2YHdJTPvStCZ8mdeyldbXAoRUUFfo7lYs+sZb+Ba
    ztAeQB9ctS2O+hgcNY5nz8Xj2efec+W+l97y7Bw==
ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=
    mail.ovh.net; h=from:to:subject:mime-version:date:message-id
    :content-type; s=arc-20240129-1; t=1759304276; bh=gCl3wBII9s781N
    jOfwqdvR76fe52yQ1GuPli9cc9MwI=; b=G5o9nK3IlRj4UrqssS4K6Gq5EeuO/8
    izQidxk1QqzvUTvBOZnnqWumRLjnX8Mk/3O2MVvwQoNjSxH227BIR69mZ7MpvDzG
    ec4ng02xfAQsiN5H8Jc8RMLvBF+Xc+JScqOj5kLrvNqafaR62+t7PpqbGNSVND8q
    1/7st3WChOCB2QAyOoTwc3aWFbk4TK2S4C9p6OY9NjcsAZcecvM+H6DbEEoskUIz
    txFjkZhpStVyCp0fglgxEwKpquIIFqn2JQKeTAWioU5uN66ZUmr0xkg24a9SJ8ta
    HQlU0iciMlLPG5oEVD4nR3gJ6jBlm4aW2/84LJmCFayf3SaFcBajSAgA==
ARC-Authentication-Results: i=1; mx.mail.ovh.net;
    arc=none (no signatures found);
    arc=none (no signatures found);
    dkim=pass (2048-bit rsa key sha256) header.d=groups.io header.i=@groups.io
    header.b=LMSWqwOL header.a=rsa-sha256 header.s=groups1;
    dmarc=pass policy.published-domain-policy=none
    policy.published-subdomain-policy=none policy.applied-disposition=none
    policy.evaluated-disposition=none (p=none,sp=none,d=none,d.eval=none)
    policy.policy-from=p header.from=groups.io;
    spf=pass smtp.mailfrom=modnoticebounce+*@groups.io
    smtp.helo=mail06.groups.io;
    x-tls=pass smtp.version=TLSv1.2 smtp.cipher=ECDHE-RSA-AES256-GCM-SHA384
    smtp.bits=256
Authentication-Results: 
Received: from output49.mail.ovh.net (unknown [10.42.17.0])
	by sandman-8498d4fd76-49jgl with LMTP id fb9mxZACmQh6fWR78ZSK53;
	for <*.be>; Wed, 01 Oct 2025 07:37:55 -0000
Received: from vr27.mail.ovh.net (unknown [10.101.8.27])
	by out49.mail.ovh.net (Postfix) with ESMTP id 4cc6GW2rMPzDqFG
	for <*@*.be>; Wed,  1 Oct 2025 07:37:55 +0000 (UTC)
Received: from in55.mail.ovh.net (unknown [10.101.4.55])
	by vr27.mail.ovh.net (Postfix) with ESMTP id 4cc6GW12zyzFpd7
	for <*@*.be>; Wed,  1 Oct 2025 07:37:55 +0000 (UTC)
Received: from mail06.groups.io (mail06.groups.io [192.53.124.123])
	by in55.mail.ovh.net (Postfix) with ESMTPS id 4cc6GV3TmmzfYm4
	for <*@*.be>; Wed,  1 Oct 2025 07:37:54 +0000 (UTC)
Authentication-Results: 
Received-SPF: pass
    (groups.io: Sender is authorized to use
 'modnoticebounce+*@groups.io' in 'mfrom' identity
 (mechanism 'include:_spf.groups.io' matched))
    receiver=in55.mail.ovh.net;
    identity=mailfrom;
    envelope-from="modnoticebounce+*+*+*+9299855@groups.io";
    helo=mail06.groups.io;
    client-ip=192.53.124.123
DKIM-Signature: a=rsa-sha256; bh=gCl3wBII9s781NjOfwqdvR76fe52yQ1GuPli9cc9MwI=;
 c=relaxed/relaxed; d=groups.io;
 h=From:Subject:Date:Message-ID:To:Cc:In-Reply-To:References:Reply-To:Sender:List-Id:List-Post:List-Subscribe:List-Unsubscribe:List-Help:MIME-Version:Content-Type:Content-Transfer-Encoding;
 s=groups1; t=1759304266; v=1; x=1759563466;
 b=LMSWqwOLBSBGtfW9j+pFzKuF4Ydq0Jy5fHPztStw1hBTcBaeGQPf6yy0bRhz8FEsKJyo9wIo
 iWitdriMzK+1tGYDX92Tsxkh1OVSTl9FhHRRjdqV9dSMdTi6Q6P9UdaNH7XvtLFPNP6BV+DJdoG
 7/czfjsZsUXR9r0xOfGPPojYS96KviYVEQY4XxfXqKOQxNd8baFIapdCWtLzJ/FE1pcRNzSIyPX
 H/wVWJ2gvwtMwqTbfvuhbjCK6PZ0n3q4yJWZfjScDqvt3e4Q2HAGgnD1SrlZRJjiOl+fdHSRGMQ
 yn4QltcgCT9L5qckWgT8zTyLBH06wftU+vJizdHIcmA9Q==
From: "Group Notification" <noreply@groups.io>

Toutes mes excuses, en effet cela fonctionne et je reçois maintenant les messages.

ARC-Message-Signature:i=1; a=rsa-sha256; c=relaxed/relaxed; d=laposte.net; s=lpn-wlmd; t=1759322877; h=Date:From:To:Subject:DKIM-Signature; bh=g3zLYH4xK xcPrHOD18z9YfpQcnk/GaJedfustWU5uGs=; b=H3YdXPdUD198VcgwQFyuTTwCWxyvu8DfGEEut V8f19Fbl4kR06V8axXqd3jVlTBB2I/a9R1z38+Wf+Qf1Adkq7EjM3yDobNrsyc2La1JM6JDFZLqh m5w4EadcV9Ble9RrwA9YqwbStGSYb6QM/