maildomain.datevnet.com has no NS records.
NS records for this zone are defined at datevnet.com.
NS records for this zone are defined at datevnet.com.
Question and response
Question
dig maildomain.datevnet.com. NS
Answer
The response has no answer records.
Authority
datevnet.com. 600 SOA ns01.datev.de. dnsmaster.datev.de. 2602250039 21600 3600 604800 600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0