mail.domtele.com has no CNAME records.
Question and response
Question
dig mail.domtele.com. NS
Answer
The response has no answer records.
Authority
domtele.com. 300 SOA ns.datagroup.com.ua. hostmaster.datagroup.com.ua. 2023042400 28800 7200 2419200 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0