mail.mail24server.de has no NS records.
NS records for this zone are defined at mail24server.de.
NS records for this zone are defined at mail24server.de.
Question and response
Question
dig mail.mail24server.de. NS
Answer
The response has no answer records.
Authority
mail24server.de. 600 SOA www.mail24server.de. root.mail24server.de. 2007052410 28800 7200 1209600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0