mail.olitt.com has no NS records.
NS records for this zone are defined at olitt.com.
NS records for this zone are defined at olitt.com.
Question and response
Question
dig mail.olitt.com. NS
Answer
The response has no answer records.
Authority
olitt.com. 1800 SOA hugh.ns.cloudflare.com. dns.cloudflare.com. 2396983044 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0