smtp2.dimenoc.com has no MX records.
Question and response
Question
dig smtp2.dimenoc.com. MX
Answer
The response has no answer records.
Authority
dimenoc.com. 14440 SOA ns1.dimenoc.com. network.dimenoc.com. 2019062997 300 300 2419200 86400
Additional
. 0 OPT ; payload 1680, xrcode 0, version 0, flags 0