mx1.megamailservers.com has no CNAME records.
Question and response
Question
dig mx1.megamailservers.com. NS
Answer
The response has no answer records.
Authority
megamailservers.com. 10462 SOA ns1.meganameservers.com. root.megamailservers.com. 508 86500 3600 3600000 345600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0