cdn.ip-only.net has no MX records.
Question and response
Question
dig cdn.ip-only.net. MX
Answer
The response has no answer records.
Authority
cdn.ip-only.net. 10800 SOA ns1.onapp.ip-only.net. johan\.caripson.ip-only.se. 2016071503 7200 900 1209600 10800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0