mx1.klicktipp.com has no MX records.
Question and response
Question
dig mx1.klicktipp.com. MX
Answer
The response has no answer records.
Authority
klicktipp.com. 1800 SOA dara.ns.cloudflare.com. dns.cloudflare.com. 2396982561 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0