VisNetic Mail Server's Instant Anti Spam employs both rules-based and challenge-response anti spam technologies, providing enterprise organizations unmatched spam filtering capability. This combination of anti spam methodologies will reduce costs associated with spam, save valuable bandwidth and protect your organization from the liabilities spam presents.

Rules-based anti spam tools employ header and text analysis to determine whether an email message is spam. Specifically, rules-based technology examines email headers for the circuitous routing spam typically takes and the subject line and body for words or phrases commonly found in spam. It then compares its findings to pre-defined or administrator-defined filters. Messages matching anti spam filter criteria are deemed spam; all others are believed legitimate.

Early rules-based software utilized algorithms for header and text analysis. Running message content through a series of hard-coded programs and procedures, these solutions resulted in Yes/No decisions-identifying each message as spam or not-spam. Subsequent action on each message-accept or reject-was dependent on whether or not it was categorized as spam.

More recently developed or enhanced rules-based solutions utilize heuristic analysis to determine the likelihood that a message is spam. Unlike algorithmic analysis, heuristic processes are not reliant upon pre-established formulas. Instead, this trial-by-error method applies rules derived from experience to determine whether a message may be spam. Heuristic analysis does not simply produce Yes/No results. Rather, each message is assigned a weight or score indicating the likelihood that the message is spam. Messages are then forwarded to a mail server or email client where administrators or users can specify score thresholds and subsequent required action-accept, reject or quarantine for independent review.

A growing number of rules-based solutions now implement Bayesian filtering, a technique combining heuristics and probability analysis, enabling the software to learn and relearn how to recognize spam by scanning the mail you've read and the mail you've rejected. Probability calculation is based on each message's most unusual characteristics. Over time, the anti spam engine learns what type of email to deliver - and what to reject or delete.

In addition to a more sophisticated method of analysis, today's rules-based anti spam solutions include white list capabilities as well as the ability to check messages against various real-time black hole lists, or RBLs-public catalogs of known spammers and open relay servers that spammers use as conduits for their messages. White lists allow mail recipients to identify pre-approved or welcomed senders, exempting them from analysis. RBL checking adds the benefit of collaborative anti spam efforts to an individual or organization's anti spam solution.

Challenge-response, or permission-based email systems, are relatively new and to date, have been available exclusively through ASPs. Gaining in popularity, these systems provide the most effective anti spam measure against computer-generated spam.

Challenge-response anti spam technology shifts the burden of effort from email recipients to email senders, by requiring them to obtain authorization to deliver their email message. If they do not complete the authorization or verification requirement, their email messages are blocked and never appear in your mailbox.

Challenge-response systems compare every inbound email message first to a white list-immediately passing email from whitelisted, or approved senders on to the recipient-and then to a black list-automatically blocking and deleting mail from blacklisted, or unapproved senders.

If the sender is on neither list, the system automatically sends an email, or challenge, explaining that you are using a "permission-based" system. The email asks the sender to go to a Web page and complete a verification task. Once completed, this sender will not be challenged again. In other words, subsequent email messages from this sender will not be subjected to your anti spam mechanism.

By integrating the best in rules-based anti spam technology with an innovative challenge-response system, Instant Anti Spam provides powerful, comprehensive anti spam protection right inside your mail server, VisNetic Mail Server.