mx4.uadns.com has no CNAME records.
Question and response
Question
dig mx4.uadns.com. NS
Answer
The response has no answer records.
Authority
uadns.com. 341 SOA ns1.uadns.com. hostmaster.drs.net.ua. 2025032801 28800 7200 3600000 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0