mail.d39s.de has no NS records.
NS records for this zone are defined at d39s.de.
NS records for this zone are defined at d39s.de.
Question and response
Question
dig mail.d39s.de. NS
Answer
The response has no answer records.
Authority
d39s.de. 1800 SOA adel.ns.cloudflare.com. dns.cloudflare.com. 2399278904 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0