cu.iskyhost.net has no MX records.
Question and response
Question
dig cu.iskyhost.net. MX
Answer
The response has no answer records.
Authority
iskyhost.net. 86400 SOA ns1.iskyhost.net. admin.iskyhost.net. 2026011401 3600 1800 1209600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0