mx.vivawebhost.com has no CNAME records.
Question and response
Question
dig mx.vivawebhost.com. NS
Answer
The response has no answer records.
Authority
vivawebhost.com. 4501 SOA ns1.vivawebhost.com. root.vivawebhost.com. 2026021700 1800 7200 2419200 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0