In real-world scenarios, false positives have ranged anywhere from 0% (none) to 0.10% depending on both implementation and users' mail behavior. Users with relatively predictable mail behavior have generally received very few false positives (less than 1 in 10,000 messages). Most false positives are likely to occur during initial training. A feature referred to as the 'training buffer' can be enabled to further water down filtering during training to help prevent false positives (see the DSPAM README for more information). Alternatively, pre-training a few hundred non-spam can also help overcome the risk of false positives during initial training. Recent versions of DSPAM are equipped with an automatic whitelisting function which whitelists senders the user receives a lot of legitimate mail from (automatically). This too helps prevent false positives during training. Everyone's email is different, however. Your mileage may vary.