smtp.clearfly.net has no CNAME records.
Question and response
Question
dig smtp.clearfly.net. NS
Answer
The response has no answer records.
Authority
clearfly.net. 511 SOA georgia.ns.cloudflare.com. dns.cloudflare.com. 2396699710 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0