mail.schwabe.de has no NS records.
NS records for this zone are defined at schwabe.de.
NS records for this zone are defined at schwabe.de.
Question and response
Question
dig mail.schwabe.de. NS
Answer
The response has no answer records.
Authority
schwabe.de. 1800 SOA ezra.ns.cloudflare.com. dns.cloudflare.com. 2397685519 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0