How to send e-mail using SmtpClient class ?

public class SendMailServlet extends HttpServlet {

    String smtpServer;

    public void init(ServletConfig config) throws ServletException {

        // get the SMTP server from the servlet properties

        smtpServer = config.getInitParameter("smtpServer");

    }

    public void doPost(HttpServletRequest req, HttpServletResponse res)
       throws ServletException,   IOException  {

        // get the message parameters from the HTML page

        String from = req.getParameter("from");

        String to = req.getParameter("to");

        String subject = req.getParameter("subject");

        String text = req.getParameter("text");

        PrintWriter out = res.getWriter();

        res.setContentType("text/html");

        try {

            // create an SMTP client

            SmtpClient smtp = new SmtpClient(smtpServer);

            // set the from and to fields

            smtp.from(from);

            smtp.to(to);

            // Get the print stream

            PrintStream message = smtp.startMessage();

            // write the message to the print stream

            message.println("From: " + from);

            message.println("To: " + to);

            message.println("Subject: " + subject);

            message.println(text);

            // close the SMTP connection and send the message

            smtp.closeServer();

            out.println("Message sent successfully.");

        }

        catch (IOException e) {

            out.println("Unexpected error.<br>" + e.getMessage());

        }

    }

}