Apparently no DKIM signature is attached to the outgoing emails. The keys were generated using OpenSSL (openssl genrsa -out private.pem 1024). SFOS acts as MTA. This is usually not great rocket science. Is there currently a known problem? There is already another discussion on this topic, but unfortunately it is already closed (Sophos XG - Smarthost - DKIM Signatur wird nicht durchgeführt).
(contoso.com would be specified as the domain if the e-mail address is firstname.lastname@example.org)
[edited by: emmosophos at 4:58 PM (GMT -7) on 1 Jun 2023]