Email messages not signed with DKIM

Problem Description
Mail-testers (specifically Port25 Verifer) are responding to my emails with dkim=none reason="message not signed"

Steps to Reproduce

  1. Login to Roundcube
  2. Compose message with subject, body and add mail-tester to recipient
  3. Send Email
  4. Received email report / test result fails dkim because message is not signed.

Expected Results
Pass dkim tests

Additional Info
Checking DNS records with dkim selector respond with a positive key result. No issues with DNS settings - they comply to plinth specified keys.

Information

  • FreedomBox version: FreedomBox version 22.26
  • Hardware: Raspberry Pi4
  • How did you install FreedomBox?: Through Debian repos

Note: Anyone with a brief description on how FBX signs emails would also be appreciated. As far as I understand, FBX doesnt use tools like OpenDKIM so I cant seem to find any online resources to actually know where I can intervene or understand what may cause the problem. Thanks again.

Looks like rspamd is resposible for signing DKIM.
in /etc/postfix/main.cf noticed

non_smtpd_milters = inet:127.0.0.1:11332
smtpd_milters = inet:127.0.0.1:11332

additionally, /var/lib/rspamd/dkim/ holds a key to the domain…

why then doesn’t rspamd sign the outgoing e-mails?

also noticed that as per DKIM signing module there should be a dkim_signing.conf file somewhere under /etc/rspamd/local.d which doesnt seem to exist…

or am I all in the wrong direction ?.. hmph…