mx.just-say-know.com has no CNAME records.
Question and response
Question
dig mx.just-say-know.com. NS
Answer
The response has no answer records.
Authority
just-say-know.com. 3519 SOA dns.just-say-know.com. hostmaster.just-say-know.com. 1906688661 43200 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0