ns5.goskope.com has no MX records.
Question and response
Question
dig ns5.goskope.com. MX
Answer
The response has no answer records.
Authority
goskope.com. 300 SOA ns1.goskope.opskope.com. hostmaster.nsone.net. 1771951977 3600 600 604800 300
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0