mail.dn-s.be has no MX records.
Question and response
Question
dig mail.dn-s.be. MX
Answer
The response has no answer records.
Authority
dn-s.be. 300 SOA nsauth.dn-s.be. hostmaster.dn-s.be. 2026011602 600 3600 1209600 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0