oraclecloud21.com has no MX records.
Question and response
Question
dig oraclecloud21.com. MX
Answer
The response has no answer records.
Authority
oraclecloud21.com. 300 SOA ns1.p200.dns.me-dcc-doha-1.oci.oraclerealm1.com. hostmaster.oraclecloud21.com. 18 3600 600 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0