Kan nogen fortælle mig hvad der er galt her

import javax.mail.*;
import javax.mail.internet.*;
import java.net.*;

import java.util.*;

/**
  * A simple email sender class.
  */
public class Test //SimpleSender
{

    /**
    * Main method to send a message given on the command line.
    */
    public static void main(String args[])
    {
        try
        {
            String smtpServer= "smtp.tiscali.dk";
            String to= "mrbonus@teamcqb.dk";
            String from= "festogfarver@hotmail.com";
            String subject="Hej";
            String body="Hejsa med digsa";

            send(smtpServer, to, from, subject, body);
    }
    catch (Exception ex)
    {
      System.out.println("Usage: java com.lotontech.mail.SimpleSender"
      +" smtpServer toAddress fromAddress subjectText bodyText");
    }

    System.exit(0);
  }

    /**
    * "send" method to send the message.
    */
    public static void send(String smtpServer, String to, String from, String subject, String body)
    {
        try
        {
            Properties props = System.getProperties();

            // -- Attaching to default Session, or we could start a new one --

            props.put("mail.smtp.host", smtpServer);
            Session session = Session.getDefaultInstance(props, null);

            // -- Create a new message --
            MimeMessage msg = new MimeMessage(session);

            // -- Set the FROM and TO fields --
            msg.setFrom(new InternetAddress(from));
            msg.setRecipients(Message.RecipientType.TO,
                InternetAddress.parse(to, false));

            // -- We could include CC recipients too --
            // if (cc != null)
            // msg.setRecipients(Message.RecipientType.CC
            // ,InternetAddress.parse(cc, false));

            // -- Set the subject and body text --
            msg.setSubject(subject);
            msg.setText(body);

            // -- Set some other header information --
            msg.setHeader("X-Mailer", "LOTONtechEmail");
            msg.setSentDate(new Date());

            // -- Send the message --
            Transport.send(msg);

            System.out.println("Besked sendt");
        }
        catch (Exception ex)
        {
            System.out.println(ex.getMessage());
            ex.printStackTrace();
        }
    }
}


den kommer med denne fejl, Exception in Thread "main" java.lang.NoClassDefFoundError: javax/activation/DataSource
at Test.send(Test.java:52)
at Test.main(Test.java:26)

det er i denne sætning
MimeMessage msg = new MimeMessage(session);

på forhånd tak