mail.dns1.de has no MX records.
Question and response
Question
dig mail.dns1.de. MX
Answer
The response has no answer records.
Authority
dns1.de. 900 SOA anycast.regdns1.de. hostmaster.partnergate.com. 2026021900 28800 7200 604800 900
Additional
. 0 OPT ; payload 1400, xrcode 0, version 0, flags 0