mail2.kuban.ru has no MX records.
Question and response
Question
dig mail2.kuban.ru. MX
Answer
The response has no answer records.
Authority
kuban.ru. 86400 SOA ns.kuban.ru. geo.ns.kuban.ru. 2025111803 28800 7200 1814400 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0