ePOST works by storing data on all participant desktops. This means that you desktop is storing some of your mail, but mail for a number of other users, too. All of the data in encrypted, however, which prevents other users from reading your mail, and vice-versa. In order to survive a failure by a participating machine, ePOST replicas all data onto multiple machines, and makes sure that a suffient number of copies of each data item are stored at all times.