[otrs-de] Emailzustellung freenet.de

Hallo, OTRS hat Probleme bei der Emailzustellung an freenet-mail Accounts. This is the xxxxxx.de program at host xxxxx.de. I'm sorry to have to inform you that your message could not be 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 kundenserver-webact.de program : host mx.freenet.de[194.97.55.192] said: 550 syntax error in header (in reply to end of DATA command) Woran könnte das liegen? Danke