Spamfire should become very accurate at identifying spam after it sees a hundred or so email messages. Your actual accuracy will vary depending on the kind of good email you receive. For example, if you work in a bank and frequently receive emails about mortgage, Spamfire may sometimes have trouble telling the difference between mortgage related email and mortgage related spam. Troublesome messages usually appear as borderline messages. Borderline good messages are released to your email program.
If you have this trouble, you can tell Spamfire to intercept borderline messages and hold them, rather than releasing them automatically to your email program. Open the Spamfire Delivery Preferences, click More Options... and make the needed settings.