cns1.knownhost.com has no MX records.
Question and response
Question
dig cns1.knownhost.com. MX
Answer
The response has no answer records.
Authority
knownhost.com. 1800 SOA cns1.knownhost.com. dns.cloudflare.com. 2397101162 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0