Bayesian Filtering

The first layer in spam defense is a Bayesian filter that statistically calculates the probability that each inbound message is spam. Because it is measuring probabilities, the Bayesian approach considers all the content in an email, both good and bad. The Bayesian filter-based engine is automatically trained and updated via a spam database that is uploaded to the server, and/or trained manually on your local network.

Heuristic Analysis

The next Anti Spam layer utilizes SpamAssassin technology to heuristically examine each message against hundreds of time-tested rules and checks. Each message receives a score based on the likelihood that it is spam. This filtering is completely automated, but spam-scoring thresholds are customizable. It also integrates directly with the Bayesian filter and offers many additional features, such as complete spam message reporting, header reporting and much more.

Challenge-Response Mechanism

The last line of defense is an optional Challenge-Response mechanism, the most foolproof spam blocking method known to block 100% of computer-generated spam. If the SpamAssassin and Bayesian filters cannot definitively prove that a message is or is not spam, a challenge message is sent to the message originator. The sender is presented with an embedded link in the message. Once the user clicks on this link and enters the displayed code, their message and all of their future messages will be allowed.

VisNetic Mail Server's Instant Anti Spam also includes white list and black list capabilities. Bypassing the Bayesian filter, email from whitelisted addresses is immediately delivered and email from blacklisted addresses is immediately deleted.