ue.dnsdocloud.com has no MX records.
Question and response
Question
dig ue.dnsdocloud.com. MX
Answer
The response has no answer records.
Authority
dnsdocloud.com. 1800 SOA ns1.virtualns.net. dns.virtualname.net. 1771459200 14400 3600 1209600 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0