发送邮件的程序出现异常，大家帮帮看一下吧

程序代码：
package mail;
import javax.mail.internet.*;
import javax.mail.* ;
import java.util.*;import java.io.*;
public class Mail {
    public Mail() {
    }
    public static void main(String [] args){
       send();
    
    }
    public static void send(){
        boolean blnError=true;
        boolean blnSend = false;        String strMailserver = "smtp.126.com";
        String strFrom = "[email protected]";
        String arrstrTo = "[email protected]";
        String strSubject = "test";
        String strMessage = "success";
                        try {
                                // 设定所要用的Mail 服务器和所使用的传输协议
                                java.util.Properties props = System.getProperties();
                                props.put("mail.host",strMailserver);
                                props.put("mail.transport.protocol","smtp");                                // 产生新的Session 服务
                               javax.mail.Session mailSession = javax.mail.Session.getDefaultInstance(props,null);
                                mailSession.setDebug(false);                               Message msg = new MimeMessage(mailSession);
                                                              // 设定传送邮件的发信人
                                msg.setFrom(new InternetAddress(strFrom));                                // 设定传送邮件至收信人的信箱
                                InternetAddress[] address = InternetAddress.parse(arrstrTo,false);
                                msg.setRecipients(Message.RecipientType.TO, address);                                // 设定信中的主题
                                msg.setSubject(strSubject);                                // 设定送信的时间
                                msg.setSentDate(new java.util.Date());                                // 设定传送信的MIME Type
                                msg.setText(strMessage);                                // 送信
                                Transport.send(msg);                                System.out.print("邮件已顺利传送到"+arrstrTo);
                                blnSend=true;
                        }catch (Exception e) {
                                if(blnError)
                                        System.out.print("发送失败");
                                blnError=false;
                                e.printStackTrace();
                        }if(blnSend){
        System.out.print("邮件发送成功！");
}else if(blnError&!blnSend){
        System.out.print("邮件发送失败！");
}    }}
在Eclipse和Jbuilder中均抛出以下异常：
Exception in thread "main" java.lang.NoClassDefFoundError: javax/activation/DataSource
    at mail.Mail.send(Mail.java:34)
    at mail.Mail.main(Mail.java:11)请高手指点小弟，不胜感激啊！！！