mx.openit.de has no NS records.
NS records for this zone are defined at openit.de.
NS records for this zone are defined at openit.de.
Question and response
Question
dig mx.openit.de. NS
Answer
The response has no answer records.
Authority
openit.de. 900 SOA ns1.plusserver.com. hostmaster.plusserver.com. 2026020403 1800 900 604800 900
Additional
. 0 OPT ; payload 1680, xrcode 0, version 0, flags 0