master.domainkunden.de has no MX records.
Question and response
Question
dig master.domainkunden.de. MX
Answer
The response has no answer records.
Authority
domainkunden.de. 300 SOA master.domainkunden.de. hostmaster.domainkunden.de. 2026022401 28800 7200 604800 300
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0