ns.pop-hannover.de has no MX records.
Question and response
Question
dig ns.pop-hannover.de. MX
Answer
The response has no answer records.
Authority
pop-hannover.de. 10800 SOA ns.asys-h.de. root.asys-h.de. 2025050501 10800 1800 604800 10800
Additional
. 0 OPT ; payload 4095, xrcode 0, version 0, flags 0