mx1.vsi.ru has no CNAME records.
Question and response
Question
dig mx1.vsi.ru. NS
Answer
The response has no answer records.
Authority
vsi.ru. 1381 SOA ns.vsi.ru. noc.vsi.ru. 2026012000 28800 7200 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0