Deine Mail Adresse kommt zurück :-(

[Martin]

Hallo,

hab dir ja geschrieben, dass ich eine Mail dir geschrieben haben, das kommt dann aber auch wieder zurück. Schau dir das mal an:

This is the Postfix program at host s004-ct-ffm-r01.ec-c.net.

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 Postfix program

[e-mail]: host mx0.gmx.de[213.165.64.100] said: 550-5.7.1 {mx047} The
    recipient does not accept mails from 'gmx.de' over foreign mailservers 550
    5.7.1 ( http://www.gmx.net/serverrules ) (in reply to RCPT TO command)

Gruß Martin