1. A method, comprising: at a server system comprising one or more processors and memory: initiating delivery of a plurality of message campaigns to a plurality of users, wherein a respective message campaign of the plurality of message campaigns includes one or more messages addressed to at least a subset of the plurality of users; receiving, from a plurality of client devices associated with the plurality of users, campaign-feedback data, wherein: the campaign-feedback data is indicative of user interaction with the messages transmitted to the plurality of client devices as part of the plurality of message campaigns; and the campaign-feedback data includes information that enables generation of campaign reports that provide quantitative information about one or more of the plurality of message campaigns; after receiving the campaign-feedback data, transmitting, to one or more remote storage systems, campaign-tracking data that is based on the campaign-feedback data; after transmitting the campaign-tracking data to the one or more remote storage systems, receiving, from a requestor, a first request for analysis of the campaign-feedback information; and in response to receiving the first request for analysis of the campaign-feedback information: obtaining a campaign report generated using the campaign-tracking data from the one or more remote storage systems; and providing the campaign report to the requestor.