login.isrv1.jsn.de has no MX records.
Question and response
Question
dig isrv1.diskstation.me. MX
Answer
The response has no answer records.
Authority
diskstation.me. 3600 SOA ddns-ns1.quickconnect.to. domain.synology.com. 1762484000 3600 300 6040000 3600
Additional
. 0 OPT ; payload 1280, xrcode 0, version 0, flags 0