mail.keyspecial.de has no MX records.
Question and response
Question
dig mail.keyspecial.de. MX
Answer
The response has no answer records.
Authority
keyspecial.de. 86400 SOA ns.keyspecial.de. hostmaster.ns.keyspecial.de. 2014031317 10800 3600 604800 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0