How does Gmail filter emails?

Gmail uses sophisticated machine learning powered by TensorFlow to filter email. The system processes millions of signals to determine whether messages reach inbox, categories, or spam.

Key factors include sender reputation tracked through sending IP and domain history, authentication via SPF, DKIM, and DMARC verification, and user engagement patterns showing how recipients interact with your mail.

Gmail heavily emphasizes individual user signals. The same message from the same sender may land in inbox for one recipient and spam for another based on their personal interaction history.

The Categories system (Primary, Social, Promotions, Updates, Forums) further sorts inbox-worthy mail based on content type. Landing in Promotions is not spam; it is appropriate categorization.

Gmail's filter learns constantly from its billions of users. Every interaction teaches it something about every sender.

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