mail.vdx.sh has no NS records.
NS records for this zone are defined at vdx.sh.
NS records for this zone are defined at vdx.sh.
Question and response
Question
dig mail.vdx.sh. NS
Answer
The response has no answer records.
Authority
vdx.sh. 1800 SOA dean.ns.cloudflare.com. dns.cloudflare.com. 2397419458 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0