1. A system for managing sessions of secure electronic correspondence between at least one sending user and at least one receiving user, the system comprising: at least one directory server; at least one electronic correspondence domiciliation server comprising a private management office for each user, for at least choosing at least one correspondence counterpart, and validating a content of a correspondence to be sent and storing the correspondence once sent; at least one server for processing the correspondence; at least one electronic correspondence certification server; wherein the at least one domiciliation server further comprises: at least one electronic correspondence sessions management module comprising at least one authorization submodule for the opening of a session between a user and his private management office on condition of verifying by request, before said opening, to at least one certification server that the user, the user's counterpart and the electronic correspondence processing servers all have identity attributes stored in a database that match or exceed preset confidence, and wherein the at least one authorization submodule is configured to authorize the opening of the session to execute an authentication function of a user of the system by verifying a matching of a code entered by the user into the domiciliation server with a single secret transmitted in two different forms by the certification server, on one hand to the domiciliation server and on the other hand to the user, this second transmission being over a communication channel which is different from that by which the user connects to the system, the output of the authentication function being a condition of a continuation of the opening of the session.