mail.vdx.network has no CNAME records.
Question and response
Question
dig mail.vdx.network. NS
Answer
The response has no answer records.
Authority
vdx.network. 3418 SOA ns0.vinehost.net. dns.vinehost.net. 2026022504 10800 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0