mail for greennetproject.de loops back to myself

---------- Original Nachricht ----------
Betreff: Undelivered Mail Returned to Sender
Datum: Fri, 15 Mar 2019 20:31:44 +0100
Von: Mail Delivery System MAILER-DAEMON@dd14606.kasserver.com
An: veranstaltungen@wandelbuendnis.org

This is the mail system at host dd14606.kasserver.com.

I'm sorry to have to inform you that your message could not
be delivered to one or more recipients. It's attached below.

For further assistance, please send mail to postmaster.

If you do so, please include this problem report. You can
delete your own text from the attached returned message.

The mail system

brigitte.reich@greennetproject.de: mail for greennetproject.de loops back to myself