relay-ix.mailprotect.be has no MX records.
Question and response
Question
dig relay-ix.combell-ops.net. MX
Answer
The response has no answer records.
Authority
combell-ops.net. 3600 SOA ns3.combell.net. hostmaster.combell-ops.net. 1772805651 10800 3600 604800 40000
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0