smtp4.rocketinternet.net has no NS records.
NS records for this zone are defined at rocketinternet.net.
NS records for this zone are defined at rocketinternet.net.
Question and response
Question
dig smtp4.rocketinternet.net. NS
Answer
The response has no answer records.
Authority
rocketinternet.net. 86400 SOA dns1.rocketinternet.net. hostmaster.rocketinternet.net. 2008112900 7200 1800 604800 86400
Additional
The response has no additional records.