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Why do emails receive a negative spam score on the Email Security Gateway?

  • Type: Knowledgebase
  • Date changed: 3 years ago
Solution #00002962

All Barracuda Spam Firewalls, all firmware versions.

Any Barracuda Spam Firewall with an active Bayesian database has the potential to mark messages with a negative spam score. The Bayesian database augments spam scores by a maximum of five points in either direction, depending on whether and how strongly it interprets that email as Spam or Not Spam. While it rarely marks a message a full five points higher or lower, low-scoring emails may also have their score lowered by the Bayesian database, resulting in scores that are less than zero. Email messages with a sub-zero score are considered by the Email Security Gateway to be very obviously not spam and are treated as legitimate messages.

Another possibility for a negative message score (-1001) is the email message size. Since spam emails are statistically smaller than normal mail, the Barracuda will not spam scan messages over a certain size for spam content (although these emails will still undergo virus scanning).

Additional Notes:
If your Bayesian database is causing spam messages to be processed with a negative score, your Bayesian database might be poisoned (possibly from frequent miscategorizations during configuration). If this is so, you should consider resetting your Bayesian database and starting over.

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