What is a “filtering engine” vs a “filtering network”?

A filtering engine is the software component that analyzes individual messages and assigns spam scores. It applies rules, runs machine learning models, and checks authentication. Tools like SpamAssassin are examples of filtering engines that can be deployed independently.

A filtering network is a distributed system that aggregates intelligence across millions of senders, recipients, and messages. Providers like Spamhaus, Barracuda, and Cloudmark operate filtering networks that share threat data globally. When one node detects a new spam campaign, that knowledge propagates across the entire network within minutes.

Most major mailbox providers combine both approaches. They run their own filtering engines locally while subscribing to filtering networks for real time threat intelligence.

The engine is the inspector at your local harbor. The network is the global shipping registry that warns every port when a dangerous vessel sets sail.