dns6.cloudns.net has no MX records.
Question and response
Question
dig dns6.cloudns.net. MX
Answer
The response has no answer records.
Authority
cloudns.net. 172800 SOA pns1.cloudns.net. support.cloudns.net. 2026021702 7200 3600 1209600 172800
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0