1. A method for displaying messages performed by a client device having one or more processors and memory storing one or more programs for execution by the one or more processors to perform the method, comprising: in response to a first user action at the client device: selecting a first viewport from a plurality of viewports; and displaying at the client device a first subset of a first plurality of messages associated with the first viewport, the first subset ordered by an first importance score calculated using a first importance predictive model; in response to a second user action at the client device; selecting a second viewport from the plurality of viewports; and displaying at the client device a second subset of a second plurality of messages associated with the second viewport, the second subset ordered by a second importance score calculated using a second importance predictive model; wherein the first and second pluralities of messages each comprise messages in a single user account of the respective user; and wherein the first and second importance predictive models are not identical.