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

  • Type: Knowledgebase
  • Date changed: one year ago
Solution #00002962

Scope:
All Barracuda Spam Firewalls, all firmware versions.

Answer:
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.

Link to This Page:
https://campus.barracuda.com/solution/50160000000H42IAAS