mx.skynet.be has no MX records.
Question and response
Question
dig mx.skynet.be. MX
Answer
The response has no answer records.
Authority
mx.skynet.be. 7200 SOA ns1.skynet.be. dnsmaster.skynet.be. 2002052880 3600 900 604800 7200
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0