mx.opusnet.com has no MX records.
Question and response
Question
dig mx.opusnet.com. MX
Answer
The response has no answer records.
Authority
opusnet.com. 600 SOA ns1.opusinteractive.io. sysadmin.opusinteractive.com. 2026012201 5400 600 1209600 5400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0