作了一个邮件程序如下：

import java.util.Properties;
import javax.mail.*;
import javax.mail.internet.*;
import javax.mail.internet.MimeMessage;

public class mail{
public static void main(String[] args) throws Exception {
Properties props=new Properties();
props.put("mail.smtp.host","192.168.42.253");
Session session=Session.getDefaultInstance(props,null);

Message msg=new MimeMessage(session);

InternetAddress addressFrom=new InternetAddress("vbul@jcct.com");
msg.setFrom(addressFrom);
InternetAddress addressTo=new InternetAddress("ky@jcct.com");
msg.setRecipient(Message.RecipientType.TO,addressTo);

msg.setSubject("text");
msg.setContent("text one","text/plain");

Transport transport=session.getTransport("smtp");
transport.send(msg);

}
}

能通过编译，但运行时提示：

Exception in thread "main" java.lang.NoClassDefFoundError:javax/activation/Data
字串8

Source
at mail.main<mail.java:13>

请问如何解决阿？

import javax.activation.*;

thinks