mx2.pavietnam.com.vn has no NS records.
NS records for this zone are defined at pavietnam.com.vn.
NS records for this zone are defined at pavietnam.com.vn.
Question and response
Question
dig mx2.pavietnam.com.vn. NS
Answer
The response has no answer records.
Authority
pavietnam.com.vn. 3600 SOA dnssec1.pavietnam.vn. hostmaster.pavietnam.com.vn. 2026030711 3600 7200 1209600 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0