System and methods are provided for receiving selection, by a user, of a subset of message clusters in a plurality of message clusters. Each message cluster is associated with a corresponding set of clustering rules. Each respective electronic message, addressed to and/or from the user, in a plurality of electronic messages is assigned to one or more of the clusters in the subset of clusters in accordance with the sets of clustering rules associated with the subset of clusters. The set of clustering rules for a first cluster in the subset of clusters (i) prevents some messages in the plurality of messages from being assigned to the first cluster and (ii) assigns messages to the first cluster without regard to content relatedness between messages in the plurality of messages and messages already in the first cluster. Messages in the first cluster are formatted for display as a single cluster graphic.