mx.byteheavy.com has no CNAME records.
Question and response
Question
dig mx.byteheavy.com. NS
Answer
The response has no answer records.
Authority
byteheavy.com. 5507 SOA ns1.he.net. hostmaster.he.net. 2025102401 10800 1800 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0