mx.slett.net has no MX records.
Question and response
Question
dig hosted.slett.net. MX
Answer
The response has no answer records.
Authority
slett.net. 3600 SOA slett.net. postmaster.slett.net. 2700000069 3600 300 86400 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0