dpmail.dev.datev.de has no NS records.
NS records for this zone are defined at dev.datev.de.
NS records for this zone are defined at dev.datev.de.
Question and response
Question
dig dpmail.dev.datev.de. NS
Answer
The response has no answer records.
Authority
dev.datev.de. 600 SOA ns01.datev.de. dnsmaster.datev.de. 2602240039 21600 3600 604800 600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0