A communication system includes a sender unit, a recipient unit and a control unit. The sender unit is adapted to generate an electronic message, to send the electronic message to the recipient unit, and to send a sending information message to the control unit indicating that the sender unit has sent the electronic message to the recipient unit. The recipient unit is adapted to receive the electronic message from the sender unit and to send a receipt information message to the control unit, the receipt information message indicating that a user of the recipient unit has received the electronic message.