mail.mc2.dev has no CNAME records.
Question and response
Question
dig mail.mc2.dev. NS
Answer
The response has no answer records.
Authority
mc2.dev. 55 SOA ns1.mc2.dev. hostmaster.mc2.dev. 2025122204 100 3600 1209600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0