pns4.clouddns.net has no MX records.
Question and response
Question
dig pns4.clouddns.net. MX
Answer
The response has no answer records.
Authority
clouddns.net. 3600 SOA pns1.cloudns.net. support.cloudns.net. 2026022804 7200 1800 1209600 3600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0