The Barracuda Spam Firewall is a stand-alone system dedicated to running programs that filter out spam and viruses from our email. All email arriving at UTPA first passes through this filter. A variety of methods are used to test email. First, the email is compared to a "blacklist" of known spammers. Most spam originates from a relatively small number of hard-core spammers, and many of their email servers are tracked by anti-spam services, who publish these blacklists. Similarly, most spammers send the same message to millions of recipients making it possible to "fingerprint" bulk mailings and then test our incoming email against that fingerprint. Finally, and most powerfully, the system employs Bayesian statistical analysis of every recipient's own email to distinguish good email from bad. The system will actually learn the difference between your own personal valid email and your spam. Every piece of incoming email is assigned a score based on these tests. Email assigned exceptionally high scores is certainly spam and is "blocked", that is, it is simply deleted. Email that is probably, but not certainly, spam is saved, but "quarantined" on the spam filter. The remaining email is probably all valid and is passed on to the email server for delivery.