mx1.na4u.ru has no CNAME records.
Question and response
Question
dig mx1.na4u.ru. NS
Answer
The response has no answer records.
Authority
na4u.ru. 13 SOA ns1.netangels.ru. hostmaster.netangels.ru. 1769619834 3600 1800 1209600 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0