Email-Problem

[Kontotekto]

Hallo,
Nun habe ich alles am Laufen und wollte mir testweise eine Mail an die Domai n adresse senden aber da kommt als antwort gleich:

This is the mail system at host computing-community.de.

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

Was muss ich umstellen damit es geht ???