javaemail的问题，急！！！！！！！！！！！！！

try{
String host = "smtp.163.com";   //发件人使用发邮件的电子信箱服务器  ，//        String from="[email protected]";//        String from="[email protected]";
   
     String  to="[email protected]"//发邮件的目的地（收件人信箱）
    
    String tile="aa";
    String contents="aa";

        // Get system properties
    Properties props = System.getProperties();     // Setup mail server
    props.put("mail.smtp.host", host);
//     Session session = Session.getDefaultInstance(props, null);
    // Get session
    props.put("mail.smtp.auth", "true"); //这样才能通过验证//     MyAuthenticator myauth = new MyAuthenticator("[email protected]", "aaa");//     MyAuthenticator myauth = new MyAuthenticator("[email protected]","aaa");     Session session = Session.getDefaultInstance(props, myauth);//     session.setDebug(true);     // Define message
    MimeMessage message = new MimeMessage(session);
         // Set the from address
    message.setFrom(new InternetAddress(from));     // Set the to address
    message.addRecipient(Message.RecipientType.TO,
      new InternetAddress(to));     // Set the subject
    message.setSubject(tile);     // Set the content
    message.setText(contents);     message.saveChanges();       Transport.send(message);

}catch(Exception e){
e.printStackTrace();
request.setAttribute("info", "服务器正忙！请稍后再试！");
}
我有两个163.com邮箱,用前面一个就发邮件成功.用另外一个发邮件就会报错;
java.lang.SecurityException: Access to default session denied
at javax.mail.Session.getDefaultInstance(Session.java:316)
at com.videog.front.FindPasswordAction.execute(FindPasswordAction.java:65)
at org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:431)
at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:236)
at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1196)
at org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:432)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:710)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:269)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)
at com.videog.util.FormEncodeFilter.doFilter(FormEncodeFilter.java:76)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:215)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:174)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:108)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:151)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:874)
at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:665)
at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:528)
at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:81)
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:689)
at java.lang.Thread.run(Unknown Source)这到底是为什么。。？？？