No DKIM signature

Mail is leaving unsigned, so DMARC has only SPF to rely on — and SPF breaks whenever a message is forwarded.

What causes it

• DKIM was never enabled in the sending platform, or the selector record was never added to DNS.

How to fix it

Enable DKIM in each sending platform and publish the selector record it gives you. Selectors cannot be enumerated from DNS, so a checker reporting "not found" after probing common selectors is suggestive, not proof — confirm the selector name in your provider dashboard.

Check your domain

Also searched for: dkim not found, dkim=none, no dkim record.