Fix · nginx
Fix “Email signing (DKIM)” on nginx
Enable DKIM at your mail provider and publish the selector record it gives you (e.g. google._domainkey / selector1._domainkey).
No server-level snippet for this control on nginx; apply the guidance below.
Verify the fix
Re-run the Email signing (DKIM) check after deploying. Test config changes in staging first and keep a rollback: a wrong header can break a site faster than a missing one.
Other stacks: Apache · Caddy · Express / Node · Cloudflare