storage.yandex.net has no MX records.
Question and response
Question
dig storage.yandex.net. MX
Answer
The response has no answer records.
Authority
storage.yandex.net. 300 SOA ns3.yandex.ru. sysadmin.yandex.ru. 1773094118 900 600 3600000 300
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0