mx-n.jpberlin.de has no NS records.
NS records for this zone are defined at jpberlin.de.
NS records for this zone are defined at jpberlin.de.
Question and response
Question
dig mx-n.jpberlin.de. NS
Answer
The response has no answer records.
Authority
jpberlin.de. 1800 SOA ns.jpberlin.de. root.jpberlin.de. 2014830915 14400 1800 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0