dns3.online.pro has no MX records.
Question and response
Question
dig dns3.online.pro. MX
Answer
The response has no answer records.
Authority
online.pro. 3600 SOA dns.online.pro. admin.online.pro. 1573108952 14400 7200 2419200 3600
Additional
. 0 OPT ; payload 1220, xrcode 0, version 0, flags 0