mx1.iomartcloud.com has no CNAME records.
Question and response
Question
dig mx1.iomartcloud.com. NS
Answer
The response has no answer records.
Authority
iomartcloud.com. 1719 SOA heracles.iomart.com. hostmaster.iomart.com. 2025100200 43200 1800 2419200 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0