spf4391.copernica.net has no NS records.
NS records for this zone are defined at copernica.net.
NS records for this zone are defined at copernica.net.
Question and response
Question
dig spf4391.copernica.net. NS
Answer
The response has no answer records.
Authority
copernica.net. 60 SOA dns1.proxi.nl. hostmaster.copernica.com. 1773858007 14400 1800 86400 60
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0