workflow.mail.em3.oraclecloud.com has no CNAME records.
Question and response
Question
dig workflow.mail.em3.oraclecloud.com. NS
Answer
The response has no answer records.
Authority
em3.oraclecloud.com. 577 SOA ns1.p201.dns.oraclecloud.net. hostmaster.oracle.com. 2026010708 7200 600 1209600 900
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0