nsbak.dotvndns.com has no MX records.
Question and response
Question
dig nsbak.dotvndns.com. MX
Answer
The response has no answer records.
Authority
dotvndns.com. 3600 SOA ns1.dotvndns.vn. hostmaster.dotvndns.com. 2024090101 14400 3600 1209600 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0