azurewebsites.net has no MX records.
Question and response
Question
dig azurewebsites.net. MX
Answer
The response has no answer records.
Authority
azurewebsites.net. 60 SOA ns1-224.azure-dns.com. msnhst.microsoft.com. 2029458736 900 300 604800 60
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0