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 from the plurality of client devices, 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 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, wherein a respective remote storage system of the one or more remote storage systems has a plurality of performance levels and the method further comprises: while using the respective remote storage system at a first performance level, determining that a different performance level for the respective remote storage system is needed; and in response to the determination that a different performance level for the respective remote storage system is needed, requesting a change in performance level of the respective remote storage system from the first performance level to a second, different performance level, wherein the performance level of the respective remote storage system includes values for one or more of: an amount of storage space available at the respective remote storage system; a speed of read access to the respective remote storage system; a speed of write access to the respective remote storage system; and shared use of storage servers at the remote storage system.