java.lang.NoClassDefFoundError: javax mail Address

java.lang.NoClassDefFoundError: javax mail Address
java.lang.Class.getDeclaredConstructors0(Native Method)
java.lang.Class.privateGetDeclaredConstructors(Class.java:2328)
java.lang.Class.getConstructor0(Class.java:2640)
java.lang.Class.newInstance0(Class.java:321)
java.lang.Class.newInstance(Class.java:303)
org.apache.struts.util.RequestUtils.applicationInstance(RequestUtils.java:143)
org.apache.struts.action.RequestProcessor.processActionCreate(RequestProcessor.java:280)
org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:218)
org.apache.struts.action.ActionServlet.process(ActionServlet.java:1194)
org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:432)
javax.servlet.http.HttpServlet.service(HttpServlet.java:709)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)

这是我的代码：

sendmailForm.getFrom(),//是谁发送的
sendmailForm.getStmphost()//邮件服务器
sendmailForm.getTo() //是发送给谁
sendmailForm.getContext(),//发送内容
sendmailForm.getTitle(),//发送标题
sendmailForm.getUser(),//用户名
sendmailForm.getPass()//密码


  try  {
  Properties  props  =  System.getProperties();
  props.put( "mail.smtp.host",sendmailForm.getStmphost());
  props.put( "mail.smtp.auth","true");

  Session  session  =  Session.getInstance(props,  null);
  MimeMessage  mimeMessage  =  new  MimeMessage(session);

  mimeMessage.setFrom(new InternetAddress(sendmailForm.getFrom()));

  mimeMessage.setRecipients(Message.RecipientType.TO,sendmailForm.getTo());
// iso-8859-1
  mimeMessage.setSubject(sendmailForm.getTitle(),"gb2312 ");
  mimeMessage.setText( sendmailForm.getContext(),"gb2312 ");
  mimeMessage.setHeader( "Content-Type ",  "text/html ");
  mimeMessage.setSentDate(new  Date());


  Transport  transport  =  session.getTransport( "smtp ");
  transport.connect(sendmailForm.getStmphost(),sendmailForm.getUser(),sendmailForm.getPass());
  transport.sendMessage(mimeMessage,  mimeMessage.getRecipients(Message.RecipientType.TO));
  //transport.send(mimeMessage);
  transport.close();
  System.out.println( "结束########################################## ");
  }
  catch  (Exception  e)  {
  e.printStackTrace();
  return mapping.findForward("error");
  }

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mail.jar包没有导入
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mail.jar activation.jar
好像是要两个包吧~
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