mail.happyfox.com has no NS records.
NS records for this zone are defined at happyfox.com.
NS records for this zone are defined at happyfox.com.
Question and response
Question
dig mail.happyfox.com. NS
Answer
The response has no answer records.
Authority
happyfox.com. 1800 SOA lisa.ns.cloudflare.com. dns.cloudflare.com. 2397944493 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0