mail.prov.org.ua has no CNAME records.
Question and response
Question
dig mail.prov.org.ua. NS
Answer
The response has no answer records.
Authority
org.ua. 448 SOA ho1.ns.org.ua. hostmaster.org.ua. 2008208114 3636 1212 1814400 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0