mail.vdxhost.com has no NS records.
NS records for this zone are defined at vdxhost.com.
NS records for this zone are defined at vdxhost.com.
Question and response
Question
dig mail.vdxhost.com. NS
Answer
The response has no answer records.
Authority
vdxhost.com. 1800 SOA michelle.ns.cloudflare.com. dns.cloudflare.com. 2398721337 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0