smail-mta2.dts.de has no NS records.
NS records for this zone are defined at dts.de.
NS records for this zone are defined at dts.de.
Question and response
Question
dig smail-mta2.dts.de. NS
Answer
The response has no answer records.
Authority
dts.de. 3600 SOA ns1.dts-online.net. hostmaster.dts-online.net. 2026030300 28800 7200 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0