Scenario:

How to use JavaMail API to send authenticated SMTP Emails?
How to use JavaMail with MX Outbound as the SMTP Provider?

Solution:

The example code below shows how to use the JavaMail API to send emails using MX Outbound as the SMTP Provider for email delivery.

import java.io.*;
import java.util.*;
import javax.activation.*;
import javax.mail.*;
import javax.mail.internet.*;

public class SendEmail {
	public static void main(String[] args) {
		// SMTP Server Details
		final String hostServer   = "mxoXXXX.mxtools.co.uk";
		final String hostPort     = "25";
		final String hostUsername = "mxo-username";
		final String hostPassword = "mxo-password";

		// Recipient's Email Address
		String toEmail            = "This email address is being protected from spambots. You need JavaScript enabled to view it.";
		
		// Sender's Email Address
		String fromEmail          = "This email address is being protected from spambots. You need JavaScript enabled to view it."; 
		String fromEmailName      = "Firstname Lastname"; 
		
		// Set the email properties
		Properties props = new Properties();
		props.put("mail.smtp.host", hostServer);		// SMTP Host
		props.put("mail.smtp.port", hostPort); 			// SMTP Port
		props.put("mail.smtp.auth", "true"); 			// SMTP Authentication Enabled
		
		// If you don't want a TLS session then comment out the below line
		props.put("mail.smtp.starttls.enable", "true"); // Enable STARTTLS
		
		// Create an authenticator object 
		Authenticator auth = new Authenticator() {
			//override the getPasswordAuthentication method
			protected PasswordAuthentication getPasswordAuthentication() {
				return new PasswordAuthentication(hostUsername, hostPassword);
			}
		};
		
		// Create the Session
		Session session = Session.getInstance(props, auth);
		
		try
	    {
			// Create the MIME Message and compose the message
			MimeMessage msg = new MimeMessage(session);
			
			// Set message headers
			msg.addHeader("Content-type", "text/HTML; charset=UTF-8");
			msg.addHeader("Content-Transfer-Encoding", "8bit");
			msg.setSentDate(new Date());

			// Add the Senders information
			msg.setFrom(new InternetAddress(fromEmail, fromEmailName));
			msg.setReplyTo(InternetAddress.parse(fromEmail, false));

			// Add the subject 
			msg.setSubject("Subject of the email goes here", "UTF-8");

			// Add the message bosy
			msg.setText("Body of the message goes here", "UTF-8");
			
			// Add the Recipients
			msg.setRecipients(Message.RecipientType.TO, InternetAddress.parse(toEmail, false));

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

			System.out.println("EMail Sent Successfully!!");
	    }
	    catch (Exception e) {
			e.printStackTrace();
	    }
	}
}

Summary of server details