An electronic business postal system comprising: a closed-access network of secure system nodes; a plurality of access portals, each access portal being associated with one or more of the system nodes and with an authentication mechanism to authenticate users and configured to provide to users, authenticated by the corresponding authentication mechanism to set up postal system accounts with postal system electronic delivery addresses, an access point to the network to send and receive electronic business mailings that include postal system electronic delivery addresses and/or physical delivery addresses; a plurality of message servers, each message server being associated with one or more access portals and configured to process the electronic business mailings received from the associated access portals to produce messages, to assign identifiers to the messages that are unique over the system, and to provide the messages to associated system nodes, and further configured to process the messages received from the associated system nodes and to provide the corresponding electronic business mailings to the associated access portals; a delivery subsystem configured to direct the messages from the system nodes associated with the sending access portals to the system nodes associated with the recipient access portals, the delivery subsystem including one or more address registries that associate respective postal system electronic delivery addresses and/or physical delivery addresses with system nodes and/or access portals; and a clearance subsystem configured to operate at the system nodes to check the integrity of the received messages and the delivery of the messages and to allow the further delivery of the messages that pass both integrity checks to the access portals, whereby the system nodes comprise an originating system node adapted to send the message and a destination system node adapted to receive the message, and, in case the message passes both integrity checks at the destination system node, the destination system node is adapted to send an acknowledgement of the receipt of the message to the originating system node and the originating system node is adapted to check the integrity of the message delivery based on the acknowledgement, and, in case the message does not pass the integrity check of the message delivery at the originating system node, the originating system node is adapted to direct the destination system node to discard the received message and to resend the message. a closed-access network of secure system nodes; a plurality of access portals, each access portal being associated with one or more of the system nodes and with an authentication mechanism to authenticate users and configured to provide to users, authenticated by the corresponding authentication mechanism to set up postal system accounts with postal system electronic delivery addresses, an access point to the network to send and receive electronic business mailings that include postal system electronic delivery addresses and/or physical delivery addresses; a plurality of message servers, each message server being associated with one or more access portals and configured to process the electronic business mailings received from the associated access portals to produce messages, to assign identifiers to the messages that are unique over the system, and to provide the messages to associated system nodes, and further configured to process the messages received from the associated system nodes and to provide the corresponding electronic business mailings to the associated access portals; a delivery subsystem configured to direct the messages from the system nodes associated with the sending access portals to the system nodes associated with the recipient access portals, the delivery subsystem including one or more address registries that associate respective postal system electronic delivery addresses and/or physical delivery addresses with system nodes and/or access portals; and a clearance subsystem configured to operate at the system nodes to check the integrity of the received messages and the delivery of the messages and to allow the further delivery of the messages that pass both integrity checks to the access portals, whereby the system nodes comprise an originating system node adapted to send the message and a destination system node adapted to receive the message, and, in case the message passes both integrity checks at the destination system node, the destination system node is adapted to send an acknowledgement of the receipt of the message to the originating system node and the originating system node is adapted to check the integrity of the message delivery based on the acknowledgement, and, in case the message does not pass the integrity check of the message delivery at the originating system node, the originating system node is adapted to direct the destination system node to discard the received message and to resend the message.