mail.nepustil.net has no CNAME records.
Question and response
Question
dig mail.nepustil.net. NS
Answer
The response has no answer records.
Authority
nepustil.net. 9223 SOA ns1.nepustil.net. hostmaster.nepustil.net. 2026030201 28800 7200 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0