Message contains invalid header

[Viktor Alders]

Hello,

I have setting up a new postfix server and a  cyrus imap server a with 
Mailscanner and spamassasin. All messages comes in the hold queue of 
postfix and will be scanned by mailscanner. Now the problem is that i 
cannot receive e-mail on this new server and i get the following message 
back:

This is the mail system at host mail

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

(expanded from
 ): data format error. Command output:
    : Message contains invalid header

What do i wrong. Has someone any suggestions. Many thanks.

Regards,
Viktor