I am getting the above exception, the code is as under, as given by you in the tutorial:-

message.saveChanges();
Transport transport = session.getTransport("smtp");
transport.connect(pop3, username, password);
transport.connect(host, username, password);
transport.sendMessage(message, message.getAllRecipients());
transport.close();

when I comment out transport.connect(host, username, password); it works fine. Does it mean that the connection is still maintained with the mail server even after using the close method. How can it be overcome. Thanks,