GoogleAppEngine Error 403
===

I have coded that gae code:

index.html
    <!DOCTYPE html>
    <html>
     <head>
      <meta charset="utf-8">
      <title>A form</title>
     </head>
     <body>
     <form action="feedback" method="post">
      
      <!-- Simple text field -->
     <label for="name">Name </label>
     <input type="text" name="name"/>
     <br/>
      
      <!-- Email -->
     <label for="email">Email </label>
     <input type="email" name="email"/>
     <br/>
      
     
      <!-- Textarea -->
     <label for="description">Description </label>
     <textarea  name="description" cols="50" rows="5">Type your comment here</textarea>
     <br/>
      
      
     <input type="submit" name="submit" value="Send Request"/>
     </form>
     </body>
    </html>

web.xml

    	<servlet>
    		<servlet-name>FeedbackServlet</servlet-name>
    		<servlet-class>at.wunderapps.servlets</servlet-class>
    	</servlet>
    	<servlet-mapping>
    		<servlet-name>FeedbackServlet</servlet-name>
    		<url-pattern>/feedback</url-pattern>
    	</servlet-mapping>
    	<welcome-file-list>
    		<welcome-file>index.html</welcome-file>
    	</welcome-file-list>
    </web-app>

servlet:

    import java.io.IOException;
    import java.util.Properties;
     
    import javax.mail.Message;
    import javax.mail.Session;
    import javax.mail.Transport;
    import javax.mail.internet.InternetAddress;
    import javax.mail.internet.MimeMessage;
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
     
    @SuppressWarnings("serial")
    public class FeedbackServlet extends HttpServlet {
     
        @Override
        protected void doPost(HttpServletRequest req, HttpServletResponse resp)
                throws ServletException, IOException {
            String name = req.getParameter("name");
            String description = req.getParameter("description");
            String email = req.getParameter("email");
            Properties props = new Properties();
            Session session = Session.getDefaultInstance(props, null);
     
            String msgBody = name  + description + email + " :EMAIL";
     
            try {
                Message msg = new MimeMessage(session);
                msg.setFrom(new InternetAddress("apps@gmail.com",
                        "Es FUNKTIONIERT!!!"));
                msg.addRecipient(Message.RecipientType.TO, new InternetAddress("my.mail@mail.com", "Your name"));
                msg.setSubject("Bestellung");
                msg.setText(msgBody);
                Transport.send(msg);
     
            } catch (Exception e) {
                resp.setContentType("text/plain");
                resp.getWriter().println("Something went wrong. Please try again.");
                throw new RuntimeException(e);
            }
     
            resp.setContentType("text/plain");
            resp.getWriter().println(
                    "Thanks you for your feedback. An Email has been send out.");
        }
    }

When I am doing localhost i get:

HTTP ERROR 403

Problem accessing /. Reason:

    FORBIDDEN

Why? 

PS.: I am running it on windows 7.