ns4.211.RU has no MX records.
Question and response
Question
dig ns4.211.RU. MX
Answer
The response has no answer records.
Authority
211.RU. 60 SOA ns.211.RU. postmaster.sibset-team.RU. 2026012704 900 900 2592000 60
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0