ocs.oraclecloud.com has no MX records.
Question and response
Question
dig ocs.oraclecloud.com. MX
Answer
The response has no answer records.
Authority
ocs.oraclecloud.com. 300 SOA ns1.p200.dns.oraclecloud.net. hostmaster.ocs.oraclecloud.com. 3403370 3600 900 31536000 1800
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0