mx.s-inform.net has no MX records.
Question and response
Question
dig mx.s-inform.net. MX
Answer
The response has no answer records.
Authority
s-inform.net. 3600 SOA ns1.s-inform.net. noc.s-inform.net. 2025091003 86400 7200 3600000 172800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0