mxs.MAIL.RU has no MX records.
Question and response
Question
dig mxs.MAIL.RU. MX
Answer
The response has no answer records.
Authority
mxs.MAIL.RU. 3600 SOA ns1.MAIL.RU. hostmaster.MAIL.RU. 3436238079 1800 900 604800 3600
Additional
. 0 OPT ; payload 512, xrcode 0, version 0, flags 0