mail.vpi-corp.com has no CNAME records.
Question and response
Question
dig mail.vpi-corp.com. NS
Answer
The response has no answer records.
Authority
vpi-corp.com. 600 SOA ns73.domaincontrol.com. dns.jomax.net. 2026021000 28800 7200 604800 600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0