mail2.kualo.com has no NS records.
NS records for this zone are defined at kualo.com.
NS records for this zone are defined at kualo.com.
Question and response
Question
dig mail2.kualo.com. NS
Answer
The response has no answer records.
Authority
kualo.com. 1800 SOA pat.ns.cloudflare.com. dns.cloudflare.com. 2399356870 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0