It appears that part of the .de zone is missing from their name servers resulting in NXDOMAIN for valid queries. "It depends on the domain name. Before the letter F (denic.de, bund.de, bild.de) everything works. After (google.de, tageszeitung.de, heise.de), it fails." https://lists.dns-oarc.net/pipermail/dns-operations/2010-May/005530.html