mx00.kundenserver.de has no NS records.
NS records for this zone are defined at kundenserver.de.
NS records for this zone are defined at kundenserver.de.
Question and response
Question
dig mx00.kundenserver.de. NS
Answer
The response has no answer records.
Authority
kundenserver.de. 600 SOA rns.ui-dns.de. dnsadmin.1und1.de. 2013099672 10800 3600 604800 600
Additional
. 0 OPT ; payload 1220, xrcode 0, version 0, flags 0