This bug can be closed. The hostname of my system was 'ubuntu-9.10'. A dot in the hostname seems to be a no go. Changed this in etc/postfix/mail.cf and the error is gone.
This bug can be closed. The hostname of my system was 'ubuntu-9.10'. A dot in the hostname seems to be a no go. Changed this in etc/postfix/mail.cf and the error is gone.