mxdf.ispgateway.de has no NS records.
NS records for this zone are defined at ispgateway.de.
NS records for this zone are defined at ispgateway.de.
Question and response
Question
dig mxdf.ispgateway.de. NS
Answer
The response has no answer records.
Authority
ispgateway.de. 2560 SOA ns.namespace4you.de. hostmaster.ns.namespace4you.de. 1771853240 86400 2048 1048576 2560
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0