Adding a DKIM List-Unsubscribe-Post entry in DKIM.cpp

[ptruessel]

Hi there. We have HMailServer installed on a Windows Server an we are running a newsletter tool with it. In order to get a CSA cert we need to add a DKIM entry called "List-Unsubscribe-Post". Unfortunately we have no experience on HMailServer scripting neighter compliling for a Windows Server. Does anybody have experience on how to get this entry into the DKIM.cpp and then running on our production server?

[RvdH]

Not to be harsh, but you simply can not do that with scripting

For hMailServer to be CSA Complaint these headers have to be defined within hMailServer code in DKIM.cpp, unfortunately 5.6.x doesn't get functional updates anymore, only security updates like OpenSSL updates.
There is a 5.7.x ALPHA branch for 'enthousiasts/long time users' where functional updates sometimes are committed, but it is unlikely your hoster would choose to run a APLHA or a custom 5.6.x build on a production server.

hMailServer is basically abandonware, see: https://www.hmailserver.com/state

[RvdH]

https://certified-senders.org/wp-conten ... Update.pdf

CSA requires that you sign at least these header fields:
• X-CSA-Complaints
• List-Unsubscribe
• List-Unsubscribe-Post
• From
• To

CSA-compliance requires 2 additional headers to be included into the DKIM header tag list: X-CSA-Complaints & List-Unsubscribe-Post

https://github.com/hmailserver/hmailserver/pull/465

Return-Path: <ruud@otherdomain.nl>
Received: from mail.otherdomain.nl (mail.otherdomain.nl [xxx.xxx.xxx.xxx])
by mail.domain.nl with ESMTPS
(version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256)
; Mon, 5 Jun 2023 21:57:56 +0200
dkim-signature: v=1; a=rsa-sha256; d=otherdomain.nl; s=mail;
c=relaxed/relaxed; q=dns/txt; h=From:Subject:Date:Message-ID:To:MIME-Version:Content-Type:Content-Transfer-Encoding:List-Unsubscribe:List-Unsubscribe-Post:X-CSA-Complaints;
bh=C6f0ERxia1HU2XfNJ3Nz9Jiyn15y+vmr2Vo2t3FSAoY=;
b=hN1rCxw62BOjF3XumX8fQE8OrRTcJ70E2/n7wmxRE9EGS7BPrsVMcuvMUr6lnqubo/zOvCOQrsgUPlxlByoIaGSaV26+WqMUd1cnIsiHnmu6SKO58S0Kc6qwOV8uL0ErIDG4jdjfClIR/qt5XqFyK9xFY7kJt1JgwZWwWQFdq4w=
X-hMailServer-Envelope-From: ruud@otherdomain.nl
Received: from localhost (localhost [127.0.0.1])
by mail.otherdomain.nl with ESMTPA
; Mon, 5 Jun 2023 21:57:54 +0200
Message-ID: <27A56468-A084-4A6C-96D9-3ED14F4164DA@mail.otherdomain.nl>
List-Unsubscribe: <mailto:ruud@otherdomain.com>
List-Unsubscribe-Post: List-Unsubscribe=One-Click
X-CSA-Complaints: ruud@otherdomain.com
MIME-Version: 1.0
From: ruud@otherdomain.nl
To: ruud@domain.nl
Date: 5 Jun 2023 21:57:54 +0200
Subject: SMTP Test account ruud@otherdomain.nl
Content-Type: text/html; charset=utf-8
Content-Transfer-Encoding: base64

[palinka]

Easy peasy.

[RvdH]

Easy peasy.

The fix itself is, but getting it in a "official" build is not, unfortunately...