mail1.netnames.com has no NS records.
NS records for this zone are defined at netnames.com.
NS records for this zone are defined at netnames.com.
Question and response
Question
dig mail1.netnames.com. NS
Answer
The response has no answer records.
Authority
netnames.com. 21600 SOA udns1.cscdns.net. hostmaster.cscdns.net. 2017101356 3600 1800 3600000 21600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0