ns3.mycloudmailbox.com has no MX records.
Question and response
Question
dig ns3.mycloudmailbox.com. MX
Answer
The response has no answer records.
Authority
mycloudmailbox.com. 3600 SOA ns1.mycloudmailbox.com. admin.sherweb.com. 77087 1800 300 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0