Embodiments of message organization and spam filtering based on user interaction are presented herein. In an implementation, user interaction with a plurality of messages in a user interface is monitored, which includes analyzing an amount of time spent by a user in interacting with each message. Subsequent messages may then be filtered based on the monitored user interaction. In another implementation, messages are processed that are received via a network using a spam filter that was generated based on monitored interaction of a user with previous messages. The processing results in a value describing a relative likelihood of importance of each of the processed message to the user. The processed messages are then arranged for display in an order, one to another, in a user interface based on respective values.