aux4.dc1.ru.itoolabs.net has no MX records.
Question and response
Question
dig aux4.dc1.ru.itoolabs.net. MX
Answer
The response has no answer records.
Authority
dc1.ru.itoolabs.net. 3600 SOA dns1.itoolabs.net. noc.itoolabs.net. 2026012001 28800 7200 604800 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0