iks-jena.net has no MX records.
Question and response
Question
dig iks-jena.net. MX
Answer
The response has no answer records.
Authority
iks-jena.net. 57600 SOA avalon.iks-jena.de. hostmaster.iks-jena.de. 2026030701 28800 3600 3600000 57600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0