mailto.stiels.de has no MX records.
Question and response
Question
dig mailto.stiels.de. MX
Answer
The response has no answer records.
Authority
stiels.de. 86400 SOA ns01.stiels.de. administrator.ns01.stiels.de. 2026011202 10800 3600 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0