mail.nsentry.de has no NS records.
NS records for this zone are defined at nsentry.de.
NS records for this zone are defined at nsentry.de.
Question and response
Question
dig mail.nsentry.de. NS
Answer
The response has no answer records.
Authority
nsentry.de. 172800 SOA ns1.nsentry.de. hostmaster.nsentry.de. 2017013000 86400 7200 3600000 172800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0