mail.pi-asp.de has no MX records.
Question and response
Question
dig mail.pi-asp.de. MX
Answer
The response has no answer records.
Authority
pi-asp.de. 900 SOA ns1.link11.de. hostmaster.link11.de. 1771582510 16384 2048 1048576 900
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0