A JavaMail exception, can you explain?

[Mark Lau]

I was testing the following JavaMail code. The compile is successful, but when I run it like
java SendMailEx smtp.myuniv.edu [e-mail] [e-mail]
I got the following exception:
Exception in thread "main" java.lang.NoClassDefFoundError: javax/mail/Address
What does this mean? And what is the problem? Thanks.
// The code is attached here.

import javax.mail.*;
import javax.mail.internet.*;
class SendMailEx
{ public static void main(String [] args) throws MessagingException
  { if(args.length<3)
    { System.out.println("Usage: java SendMailEx smtpHost fromAddress toAddress");
      System.exit(1);
    }
    String smtpHost=args[0];
    String from=args[1];
    String to=args[2];
    // start a session
    java.util.Properties properties=System.getProperties();
    Session session=Session.getInstance(properties, null);
    // construct a msg
    MimeMessage message=new MimeMessage(session);
    message.setFrom(new InternetAddress(from));
    message.addRecipient(Message.RecipientType.TO, new InternetAddress(to));
    message.setSubject("JavaMailExample");
    message.setText("Hiya, how is going?");
    // connect to the transport
    Transport transport=session.getTransport("smtp");
    transport.connect(smtpHost, " ", " ");
    // send the msg and close the connection
    transport.sendMessage(message, message.getAllRecipients());
    transport.close();
  }
}

[William Brogden]

It means what it says - for some reason it can't find the Address class. Possibly a problem with Classpath. What environment did you compile it in?
Bill

[Mark Lau]

I compiled it under W2k Professional. I just copied the mail.jar and activiation.jar files from the tomcat directory to JDK_HOME\jre\lib\ext. Is this fine?