smtp02.apac.sabacloud.com has no MX records.
Question and response
Question
dig smtp02.apac.sabacloud.com. MX
Answer
The response has no answer records.
Authority
apac.sabacloud.com. 1800 SOA dns1.p01.nsone.net. hostmaster.nsone.net. 1735294303 3600 600 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0