appoci.oracle.com has no MX records.
Question and response
Question
dig appoci.oracle.com. MX
Answer
The response has no answer records.
Authority
appoci.oracle.com. 900 SOA ns1.p201.dns.oraclecloud.net. hostmaster.oracle.com. 2026020101 7200 600 1209600 900
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0