Context

OpenDKIM is not able to verify DKIM on inbound emails as it's not able to retrieve public key from DNS. The following error logs are observed in logs key retrieval failed - query timed out

Expected Behavior

OpenDKIM should be able to download public key from DNS.

Actual Behavior

OpenDKIM appears to be using root name servers instead of the name servers defined in /etc/resolv.conf. This breaks DNS in environments where outbound firewall rules restrict access to specific name servers (ie. those defined in /etc/resolv.conf).

Possible Fix

Set the Nameservers parameter in /etc/opendkim.conf to the name servers defined in /etc/resolv.conf