oci.oraclecloud.com has no MX records.
Question and response
Question
dig oci.oraclecloud.com. MX
Answer
The response has no answer records.
Authority
oci.oraclecloud.com. 300 SOA ns1.p200.dns.oraclecloud.net. hostmaster.oci.oraclecloud.com. 2038786462 3600 900 31536000 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0