b.myradns.net has no MX records.
Question and response
Question
dig b.myradns.net. MX
Answer
The response has no answer records.
Authority
myradns.net. 180 SOA a.myradns.net. support.myracloud.com. 3545875578 3600 900 2419200 180
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0