mail.byggvir.de has no NS records.
NS records for this zone are defined at byggvir.de.
NS records for this zone are defined at byggvir.de.
Question and response
Question
dig mail.byggvir.de. NS
Answer
The response has no answer records.
Authority
byggvir.de. 150 SOA ns3.stratoserver.net. hostmaster.strato-rz.de. 2020051302 86400 7200 604800 300
Additional
. 0 OPT ; payload 1220, xrcode 0, version 0, flags 0