Every .dk domain that delegates its _acme-challenge name to 2fd72b6b-fa7b-4daa-ada9-c9ed9cff02d2.auth.zigza.com. Such CNAMEs hand DNS-01 certificate validation to a shared service, so this list shows who issues TLS certificates through it. Data comes from our own scanners, which re-resolve every .dk domain in the zone roughly once a week.