I disabled diversion and skynet, the router DNS is unbound.
DKIM passes, encoding/format is faulty:
Date: Fri, 17 Nov 2023 14:32:31 +0100
To: djrEXr4DjZ2CAP@dkimvalidator.com
MIME-Version: 1.0
Message-ID: <41-65576b80-d-677bcc00@203232121>
Subject: =?utf-8?q?T=C3=84SCHT?=
User-Agent: SOGoMail 5.9.0
X-Last-TLS-Session-Version: None
——==-OpenGroupware_org_NGMime-65-1700227951.204159-2——
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: quoted-printable
sogo html text, signatur and footer mit umlaute
=C3=A4=C3=B6=C3=BC=C3=9F
–=C2=A0
signature plain text =C3=B6=C3=A4=C3=BC=C3=9F
plain footer
=C3=B6=C3=A4=C3=BC=C3=9F
——==-OpenGroupware_org_NGMime-65-1700227951.204159-2——
Content-Type: text/html; charset=utf-8
Content-Transfer-Encoding: quoted-printable
<html>sogo html text, signatur and footer mit umlaute<br />=C3=A4=C3=B6=C3=BC=
=C3=9F<br /><br />– <br />signature plain text =C3=B6=C3=A4=C3=BC=C3=9F</=
html>
html footer
=C3=B6=C3=A4=C3=BC=C3=9F
——==-OpenGroupware_org_NGMime-65-1700227951.204159-2——–
What is this ——==-OpenGroupware_org_NGMime-65-1700227951.204159-2——– about?