mx.sitevalley.com has no CNAME records.
Question and response
Question
dig mx.sitevalley.com. NS
Answer
The response has no answer records.
Authority
sitevalley.com. 3375 SOA dns1.swiftycdn.net. hostmaster.swiftycdn.net. 2021111744 7200 3600 86400 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0