srv-net.de has no MX records.
Question and response
Question
dig srv-net.de. MX
Answer
The response has no answer records.
Authority
srv-net.de. 300 SOA ns1.routing.net. hostmaster.routing.net. 2024110500 3600 3600 86400 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0