*.westus3.azure.ylw.efscloud.net has no MX records.
Question and response
Question
dig *.westus3.azure.ylw.efscloud.net. MX
Answer
The response has no answer records.
Authority
efscloud.net. 900 SOA ns1.efscloud.net. efscloud.net.domainsbyproxy.com. 393 600 300 3600000 900
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0