javamail 发邮件出现错误，帮我看看，谢谢了！~~

1、我下载了sun的javamail，并将mail.jar 复制到了lib目录下，重启动了服务器。2、我直接在jsp里发邮件，代码如下<%@page contentType="text/html;charset=utf-8"%> 
<%@ page import="javax.mail.*, javax.mail.internet.*,java.util.*"%>
　　<html>
　　<head>
　　　<title>JavaMail 电子邮件发送</title>
</head>
<body>
<%
Properties props = new Properties(); 
Session sendMailSession;
Transport transport; 
sendMailSession = Session.getInstance(props,null); Message newMessage = new MimeMessage(sendMailSession); 
newMessage.setFrom(new InternetAddress("[email protected]")); 
newMessage.setRecipient(Message.RecipientType.TO, new InternetAddress("[email protected]")); 
newMessage.setSubject("subject"); 
newMessage.setSentDate(new Date()); 
newMessage.setText("text"); props.put("mail.smtp.host","smtp.126.com");//存储发送邮件服务器的信息
props.put("mail.smtp.auth","true");//同时通过验证
transport = sendMailSession.getTransport("smtp"); 
transport.send(newMessage); 
%>
</BODY>
</HTML>
3、提示错误如下：type Exception reportmessage description The server encountered an internal error () that prevented it from fulfilling this request.exception org.apache.jasper.JasperException: Exception in JSP: /mail.jsp:1411: Transport transport; 
12: sendMailSession = Session.getInstance(props,null); 
13: 
14: Message newMessage = new MimeMessage(sendMailSession); 
15: newMessage.setFrom(new InternetAddress("[email protected]")); 
16: newMessage.setRecipient(Message.RecipientType.TO, new InternetAddress("[email protected]")); 
17: newMessage.setSubject("subject"); 
Stacktrace:
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:504)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:375)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
root cause javax.servlet.ServletException: javax/activation/DataSource
org.apache.jasper.runtime.PageContextImpl.doHandlePageException(PageContextImpl.java:858)
org.apache.jasper.runtime.PageContextImpl.handlePageException(PageContextImpl.java:791)
org.apache.jsp.mail_jsp._jspService(mail_jsp.java:78)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:97)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:332)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
root cause java.lang.NoClassDefFoundError: javax/activation/DataSource
org.apache.jsp.mail_jsp._jspService(mail_jsp.java:58)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:97)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:332)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
note The full stack trace of the root cause is available in the Apache Tomcat/5.5.17 logs.