JavaMail API - null pointer exception

I'm having trouble trying to implement the JavaMail API on our 400 (an 830
running V5R1, most likely not very up-to-date on PTF's).

I'm working with Bob Cancilla and some others on Ignite400 to come up with
a tutorial for writing an RPG wrapper for JavaMail (you can see what I've
done so far here:
http://www.estes-express.com/rpgjavamail/instructions.html)

Anyway, the Java program is throwing an exception, so I'm trying to call it
from the command line in QSH.

Here is the stack trace when it catches the exception:

java.lang.NullPointerException

javax/mail/Transport.send0(Ljavax/mail/Message;[Ljavax/mail/Address;)V+
0 (Transport.java:109)
      javax/mail/Transport.send(Ljavax/mail/Message;)V+0
(Transport.java:79)

JavaMail.sendMail(Ljava/lang/String;Ljava/lang/String;Ljava/lang/String
;Ljava/lang/String;Ljava/lang/String;)S+0 (JavaMail.java:33)
      JavaMail.main([Ljava/lang/String;)V+0 (JavaMail.java:14)

Here is the code (please note, this will not match the JavaMail.java file
on my site):

/*******************************************************************************************
     Date       : 11/02/2001
     Programmer : James Zhang
     Desc       : Practice the javamail.
********************************************************************************************/
import java.util.Properties;
import javax.mail.*;
import javax.mail.internet.*;
import java.io.*;

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

    String from     = args[0];
    String to       = args[1];
    String replyTo  = args[2];
    String subject  = args[3];
    String text     = args[4];
     short returnCode = 0;
     try{
          returnCode = sendMail(from,to,replyTo,subject,text);
     }catch(Exception e){
          e.printStackTrace();
     }
}

  public static short sendMail (String from, String to, String replyTo,
                                String subject,String text) throws
Exception {
     try{
          //get the properties
          FileInputStream     emailPropertyFile;
          //get the properties
          Properties emailProperty = new Properties();
          try{
               emailPropertyFile = new FileInputStream
("JavaMail.properties");
          }catch(FileNotFoundException e){
               //JZEmail.properties not found
               return 100;
          }
          emailProperty.load(emailPropertyFile);
          emailPropertyFile.close();

          //String host = "SMTP.RICAINS.COM";
          String hostName = emailProperty.getProperty("email.hostname");
          String hostType = emailProperty.getProperty("email.hosttype");

     // Get system properties
     Properties systemProperty = System.getProperties();

     // Setup mail server
     systemProperty.put(hostType, hostName);

     // Get session
     Session session = Session.getDefaultInstance(systemProperty, null);
          //Session session = Session.getInstance(systemProperty, null);


     // Define message
     MimeMessage message = new MimeMessage(session);

          // Set the from address
          message.setFrom(new InternetAddress(from));

          // Set the to address
          message.addRecipient(Message.RecipientType.TO, new
InternetAddress(to));

          // Set the subject
          message.setSubject(subject);

          // Set the content
          message.setText(text);

          // Set the reply to
          replyTo = replyTo.trim();
          if(replyTo != null && !replyTo.equals("")){
               InternetAddress ReplyTo[] = new InternetAddress[1];

               ReplyTo[0] = new InternetAddress(replyTo);
               message.setReplyTo(ReplyTo);
          }

          // Send message
          Transport.send(message);

     }catch(MessagingException me){
          // search for the real exception that caused the problem
          Exception realException = me;
          while ( (realException instanceof MessagingException) &&
               ((MessagingException)realException).getNextException() !=
null) {
                    realException =
((MessagingException)realException).getNextException();
          }

          // map the exceptions to error codes
          if (realException instanceof javax.mail.MessagingException)
               return 101;
          else if (realException instanceof java.net.ConnectException)
               return 102;
          else if (realException instanceof java.net.UnknownHostException)
               return 103;

     }catch(Exception e){
     // filename is not found
     e.printStackTrace();
          return 999;
     }
    return 0;
  }
}


Here is my CLASSPATH:

/JavaUtil/JavaMail/activation.jar:/JavaUtil/JavaMail/imap.jar:/JavaUtil/JavaM
ail/mail.jar:/JavaUtil/JavaMail/mailapi.jar:/JavaUtil/JavaMail/smtp.jar:/Java
Util/JavaMail/

Here is how I'm calling the program:

java JavaMail meovino@estes-express.com webmaster@estes-express.com
meovino@estes-express.com "this is subject 4" "this is the body"

Also, I have imported this code, activation.jar and mail.jar into VA for
Java, set the CLASSPATH accordingly, and it all works on my PC.  If I
export the JavaMail.class and move it to the 400, I get the same exception.
This is the first thing I've ever really tried to do (other than "hello
world" stuff) in Java, so I apologize in advance if I've missed something
basic.

Thanks in advance!
Mike E.