mailin.rbg.tum.de has no NS records.
NS records for this zone are defined at rbg.tum.de.
NS records for this zone are defined at rbg.tum.de.
Question and response
Question
dig mailin.rbg.tum.de. NS
Answer
The response has no answer records.
Authority
rbg.tum.de. 3600 SOA tuminfo1.rbg.tum.de. rbg-system.rbg.tum.de. 46001 86400 3600 2419200 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0