mail.ip.net.ua has no CNAME records.
Question and response
Question
dig mail.ip.net.ua. NS
Answer
The response has no answer records.
Authority
ip.net.ua. 10800 SOA ns1.ip.net.ua. hostmaster.ip.net.ua. 2026012700 86400 14400 1209600 172800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0