mail.localdns.com has no NS records.
NS records for this zone are defined at localdns.com.
NS records for this zone are defined at localdns.com.
Question and response
Question
dig mail.localdns.com. NS
Answer
The response has no answer records.
Authority
localdns.com. 1800 SOA ian.ns.cloudflare.com. dns.cloudflare.com. 2397956606 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0