rns.ui-dns.de has no MX records.
Question and response
Question
dig rns.ui-dns.de. MX
Answer
The response has no answer records.
Authority
ui-dns.de. 600 SOA ns-de.ui-dns.de. dnsadmin.ionos.com. 2011022155 28800 7200 604800 600
Additional
. 0 OPT ; payload 1220, xrcode 0, version 0, flags 0