mail.ext.aetzer.de has no MX records.
Question and response
Question
dig mail.ext.aetzer.de. MX
Answer
The response has no answer records.
Authority
aetzer.de. 3600 SOA ns.inwx.de. hostmaster.inwx.de. 2026022200 10800 3600 1209600 3600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0