请教：Javamail一个小错误

[alongines]

我的程序是这样的：
package org.zl.javamail;

import java.util.Properties;

import javax.mail.Address;
import javax.mail.Message;
import javax.mail.Session;
import javax.mail.Transport;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;

public class Demo01 {

public static void main(String[] args) throws Exception{

Properties props = new Properties() ;
props.setProperty("mail.smtp.auth", "true") ;
props.setProperty("mail.transport.protocol", "smtp") ;
Session session = Session.getInstance(props) ;
session.setDebug(true) ;

Message msg = new MimeMessage(session) ;
msg.setFrom(new InternetAddress("[e-mail]")) ;
msg.setText("你好，这是使用Java做的一个小程序发的邮件!") ;

Transport transport = session.getTransport() ;
transport.connect("smtp.sina.com",25,"zhanggnol_test","1111111") ;
transport.sendMessage(msg,new Address[]{new InternetAddress("[e-mail]")}) ;
transport.close() ;
}

}


编译没错，但是运行的时候就有错：
DEBUG: setDebug: JavaMail version 1.4.1
Exception in thread "main" java.lang.NoClassDefFoundError: javax/activation/DataSource
at .Demorg.zl.javamailo01.main(Demo01.java:22)

请问：怎么回事啊？

[alongines]

应该是环境变量配置错了吧