用javaMail发送邮件，抛javax.mail.MessagingException: 500 Error: bad syntax异常

Question

用javaMail发送邮件，老是抛异常，大家帮忙看看啊~  
 
public  void  doGet(HttpServletRequest  request,  HttpServletResponse  response)  throws  
                       ServletException,  IOException  {  
               response.setContentType(CONTENT_TYPE);  
               PrintWriter  out  =  response.getWriter();  
               String  host=request.getParameter("host");  
               String  from=request.getParameter("from");  
               String  to=request.getParameter("to");  
               String  subject=request.getParameter("subject");  
               String  message=request.getParameter("message");  
               String  password="用户名";  
               String  username="密码";  
                 
               Properties  pro=new  Properties();  
               pro.put("mail.transport.protocol","smtp");  
               pro.put("mail.smtp.host",host);  
               pro.put("mail.smtp.port","25");  
               pro.put("mail.smtp.auth","true");  
               try{  
                       PopupAuthenticator  popAuthenticator  =  new  PopupAuthenticator();  
                       popAuthenticator.performCheck(username,password);  
                       Session  mailsession=Session.getInstance(pro,popAuthenticator);  
 
                       Message  msg  =  new  MimeMessage(mailsession);  
                       msg.setFrom(new  InternetAddress(from));  
                       msg.setRecipients(Message.RecipientType.TO,InternetAddress.parse(to));  
                       msg.setSentDate(new  Date());  
                       msg.setSubject(subject);  
                       msg.setText(message);  
                 
                       msg.writeTo(System.out);  
                     //  System.out.println("1111111111111111111111111111");  
                       Transport.send(msg);//这里抛异常，郁闷的很  
 
                       out.println("成功发送邮件到"+to);  
                         
               }catch(MessagingException  ee){  
                       ee.printStackTrace();  
                       out.println("发送邮件失败");  
               }  
               out.close();  
       }  
 
 public  class  PopupAuthenticator  extends  Authenticator  
               {  
                               String  username=null;  
                               String  password=null;  
 
                               public  PopupAuthenticator(){}  
 
                               public  PasswordAuthentication  performCheck(String  user,String  pass)  
                               {  
                                               username  =  user;  
                                               password  =  pass;  
                                               return  getPasswordAuthentication();  
                               }  
 
                               protected  PasswordAuthentication  getPasswordAuthentication()  
                               {  
                                               return  new  PasswordAuthentication(username,  password);  
                               }  
           }  
异常-----------------  
dsfjavax.mail.SendFailedException:  Sending  failed;  
   nested  exception  is:    
           javax.mail.MessagingException:  500  Error:  bad  syntax  
 
 
           at  javax.mail.Transport.send0(Transport.java:219)  
 
           at  javax.mail.Transport.send(Transport.java:81)  
 
           at  javamail2.Servlet1.doGet(Servlet1.java:59)  
 
           at  javamail2.Servlet1.doPost(Servlet1.java:73)  
 
           at  javax.servlet.http.HttpServlet.service(HttpServlet.java:709)  
 
           at  javax.servlet.http.HttpServlet.service(HttpServlet.java:802)  
 
           at  org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:237)  
 
           at  org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:157)  
 
           at  org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:214)  
 
           at  org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)  
 
           at  org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)  
 
           at  org.apache.catalina.core.StandardContextValve.invokeInternal(StandardContextValve.java:198)  
 
           at  org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:152)  
 
           at  org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)  
 
           at  org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)  
 
           at  org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:137)  
 
           at  org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)  
 
           at  org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117)  
 
           at  org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:102)  
 
           at  org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)  
 
           at  org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)  
 
           at  org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)  
 
           at  org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)  
 
           at  org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:929)  
 
           at  org.apache.coyote.tomcat5.CoyoteAdapter.service(CoyoteAdapter.java:160)  
 
           at  org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:799)  
 
           at  org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Protocol.java:705)  
 
           at  org.apache.tomcat.util.net.TcpWorkerThread.runIt(PoolTcpEndpoint.java:577)  
 
           at  org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:683)  
 
           at  java.lang.Thread.run(Thread.java:534)