Every .dk domain that delegates its _acme-challenge name to ac.25e00864f6ee9b9920b46d653b2f4852.unitedtickets.dk.validate-akdv.net. 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.