Systems and methods for clustering electronic messages are disclosed. In some implementations, a method includes, at a computing device, responsive to a determination that a message body of a first electronic message satisfies a set of content-based clustering rules associated with a first message cluster, assigning the electronic message to the message cluster. A cluster graphic is displayed for the message cluster. The cluster graphic is characterized by (a) a first state in which messages in the message cluster are individually depicted and (b) a second state, which replaces the first state upon user input and collectively represents a plurality of messages in the message cluster. Each message in the message cluster is either (i) addressed at least to a first recipient or (ii) originates from the first recipient.