ns6.skynet.be has no MX records.
Question and response
Question
dig ns6.skynet.be. MX
Answer
The response has no answer records.
Authority
skynet.be. 3600 SOA ns1.skynet.be. dnsmaster.skynet.be. 2002088812 1200 3600 604800 3600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0