mail.directadmin.dev has no CNAME records.
Question and response
Question
dig mail.directadmin.dev. NS
Answer
The response has no answer records.
Authority
directadmin.dev. 1779 SOA macy.ns.cloudflare.com. dns.cloudflare.com. 2396677929 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0