A messaging system may enable a server to assign unique identifiers to a plurality of clients. These identifiers enable a client to determine whether a message is specifically targeted to that client or, as an alternative, whether the client is a member of a group of targeted clients. In one embodiment, each client includes a client identifier that may include code portions that are common to other members of a particular addressable client group. In addition, the client may include agents devoted to particular functions that may be uniquely addressable by the server.