mail.textapp.net has no NS records.
NS records for this zone are defined at textapp.net.
NS records for this zone are defined at textapp.net.
Question and response
Question
dig mail.textapp.net. NS
Answer
The response has no answer records.
Authority
textapp.net. 1800 SOA gabriel.ns.cloudflare.com. dns.cloudflare.com. 2397262932 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0