mail.crystalcoding.org has no CNAME records.
Question and response
Question
dig mail.crystalcoding.org. NS
Answer
The response has no answer records.
Authority
crystalcoding.org. 1715 SOA arturo.ns.cloudflare.com. dns.cloudflare.com. 2397188082 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0