Mail rejected, Mail blocked. 554 Sorry, this message appears to be spam
You may have the spam filter set to remove all spam. But this is allowing anything that the spam filter thinks might be spam to be deleted.
You may want to A) change the "Spam Check" level to a less aggressive setting.
The first option will help make less good mail as spam. The second option will allow the mail marked as spam to be marked that way only and not rejected because of it.