Can you be more specific?
What is your Barracuda model? what is your actual connection setup/routing?
With all due respect to your experience, is Barracuda dasied to your mail server? Is Spam Filtering Enabled? are you using the system defaults (Activated with Yes/No option)?
You may have to manualy set your black list for those without e-mails, assuming you meant that you are getting mail for non existing accounts?
Have you tested manually configuring Spam Scoring?