mail.flursy.com has no NS records.
NS records for this zone are defined at flursy.com.
NS records for this zone are defined at flursy.com.
Question and response
Question
dig mail.flursy.com. NS
Answer
The response has no answer records.
Authority
flursy.com. 3601 SOA dns1.registrar-servers.com. hostmaster.registrar-servers.com. 1771952803 43200 3600 604800 3601
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0