How does the service detect spam?
As with our virus protection, Google leverages visibility into billions of daily message connections to monitor spam attacks, and blocks the most obvious spam. Our heuristic engine then filters the incoming mail traffic and captures any suspicious messages. This is all performed in real-time (processed in RAM memory in our data centers) without delays to your email delivery. With these capabilities, Google combines an extremely effective capture rate with an exceptionally low false-positive rate.
