Every .dk domain that delegates its _acme-challenge name to 1d07f637-adf2-46a9-b17d-e81ccf925c9a.auth.acme-challenge.dk. 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.