esa01.ap.cmail.ondemand.com has no MX records.
Question and response
Question
dig esa01.ap.cmail.ondemand.com. MX
Answer
The response has no answer records.
Authority
cmail.ondemand.com. 300 SOA ns1.sap.net. dns.sap-ag.de. 1765449445 3541 600 3600000 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0