Every .dk domain that delegates its _acme-challenge name to 534c887c-65cc-427d-a0d0-c7d68276f7c4.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.