mail.openair.com has no MX records.
Question and response
Question
dig mail.openair.com. MX
Answer
The response has no answer records.
Authority
openair.com. 900 SOA ns1.p201.dns.oraclecloud.net. hostmaster.oracle.com. 2026012001 10800 3600 604800 900
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0