mx2.triara.com has no NS records.
NS records for this zone are defined at triara.com.
NS records for this zone are defined at triara.com.
Question and response
Question
dig mx2.triara.com. NS
Answer
The response has no answer records.
Authority
triara.com. 600 SOA dns1.triara.com. webmaster.triara.com. 2018092361 7200 7200 604800 10800
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0