mail.ostendis.ch has no MX records.
Question and response
Question
dig mail.ostendis.ch. MX
Answer
The response has no answer records.
Authority
ostendis.ch. 300 SOA ch.ch-inter.net. philippe\.moser.gmx.net. 2025091101 3600 1800 604800 300
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0