mail.cert.ee has no CNAME records.
Question and response
Question
dig mail.cert.ee. NS
Answer
The response has no answer records.
Authority
cert.ee. 2826 SOA ns.cert.ee. hostmaster.cert.ee. 2026021903 28800 7200 2419200 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0