mx.donpac.RU has no CNAME records.
Question and response
Question
dig mx.donpac.RU. NS
Answer
The response has no answer records.
Authority
donpac.RU. 2111 SOA ns0.donpac.RU. dnsmaster.donpac.RU. 2025090401 43200 7200 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0