mel1.oracleemaildelivery.com has no MX records.
Question and response
Question
dig mel1.oracleemaildelivery.com. MX
Answer
The response has no answer records.
Authority
mel1.oracleemaildelivery.com. 300 SOA ns1.p68.dns.oraclecloud.net. hostmaster.mel1.oracleemaildelivery.com. 725227 3600 600 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0