菜鸟; javamail编写的smtp发送邮件小程序，向163发送邮件失败 求救

初学者; javamail编写的smtp发送邮件小程序，向163发送邮件失败 求救
我用此小程序发送邮件到sohu是可以发送成功的，但是向163发送时却遇到这样的错误提示：
553   Requested   action   not   taken:   Local   user   only,smtp1,wKjRC7Dr+AGpORxGgCA5FA==.12289S2   1176254
  请问是什么原因？
    如果是因为身份验证的原因的话，我已经加入身份验证的部分了
源程序如下：
import   javax.mail.*;
import   javax.mail.internet.*;
import   java.util.*;
import   javax.mail.Authenticator;
import   java.io.*;

public   class   SimpleSmtpClient
{
String   smtpServer;
String   to;
String   from;
String   subject;
String   body;
String   username;
String   password;

public   SimpleSmtpClient(){
setup();
log( "Constructor   complete ");
}
private   void   setup()
{
smtpServer= "smtp.163.com ";
to= "50971231@163.com ";
from= "50971231@sohu.com ";
subject= "Unleased   book   example ";
body= "This   is   a   test   to   see   if   we   can   send   a   messge/double   test   ";
username= "50971231 ";
password= "******* ";
log( "setup   completed ");
}
  private   void   send()
{
  try{
  log( "Sending   a   message   to   "+to);
  Properties   props=System.getProperties();

  props.put( "mail.smtp.host ",smtpServer);
                          props.put( "mail.smtp.user ", "50971231 ");
  props.put( "mail.debug ", "true ");
  StupidAuthenticator   sa=new   StupidAuthenticator();
  Session   session   =Session.getDefaultInstance(props,sa);

  Message   msg=new   MimeMessage(session);

  msg.setFrom(new   InternetAddress(from));
  msg.setRecipients(Message.RecipientType.TO,InternetAddress.parse(to,false));

  msg.setSubject(subject);
  msg.setText(body);

  msg.setSentDate(new   Date());
  Transport   transport   =session.getTransport( "smtp ");
  transport.connect(smtpServer,username,password);
  transport.sendMessage(msg,msg.getAllRecipients());
  transport.close();


  System.out.println( "Message   was   sent ");

  }catch(Exception   e)
{  
  log( "Error   sending   message "+e);
}
}


private   void   log(String   s)
{
System.out.println(s);

}

public   static   void   main(   String   args[])
{
SimpleSmtpClient   sc=new   SimpleSmtpClient();

sc.send();

System.out.println( "SimleSmtpClient     is   done ");
}
}


------解决方案--------------------
应该是本地用户才能发送吧
------解决方案--------------------
smtpServer= "smtp.163.com ";
to= "50971231@163.com ";

props.put( "mail.smtp.host ",smtpServer);
props.put( "mail.smtp.user ", "50971231 ");