Q:

How to share the same email session between all instances of the application? 

Maybe this question is already answered, but I couldn't find the proper answer. 
I have a web application based in JSF, and I want to share the same email session between all the instances of the application, yet I haven't found how to do that. 
My questions are:
a) What I am thinking is stupid?  Should I just create a new session every time that I want to send a new mail? 
b) If a is false, is there a proper way to do that? 
Additional info: I'm working with PrimeFaces 4.0, Apache Tomcat 7.0.41, and JDK 7. 
EDIT: I'm establishing an email connection like this (using sun's java mail)
    Properties datos = new Properties();
    datos.put("mail.smtp.host", "smtp.gmail.com");
    datos.setProperty("mail.smtp.starttls.enable", "true");
    datos.setProperty("mail.smtp.port", "587");
    datos.setProperty("mail.smtp.user", usuarioAutenticacion);
    datos.put("mail.smtp.timeout", 5000);
    System.out.println(usuarioAutenticacion + " - " + contrasenaAutenticacion);
    sesionCorreo = Session.getDefaultInstance(datos, null);
    sesionCorreo.setDebug(true);

    try {
        conexionCorreo = sesionCorreo.getTransport("smtp");
    } catch (NoSuchProviderException ex) {
        Logger.getLogger(NotificacionesManager.class.getName()).log(Level. SEVERE, null, ex);
    }
    try {
        conexionCorreo.connect(usuarioAutenticacion, contrasenaAutenticacion);

Then I proceed to send the messages in the Queue, but I'm looking for a way for just set that connection once then start sending the mails in the queue when necessary. 

A:

The way that the Java EE designers intended you to do this is that you configure your javax.mail. Session object in your server.  This is described in the Tomcat 7 JavaMail Sessions documentation. 
Your managed beans should then be able to access the session via @Resource:
class MyManagedBean {

    @Resource(name="mail/Session") // this name is defined by your configuration
    private Session mailSession;

    public void someBusinessMethod() {
         ...
         Message message = new MimeMessage(mailSession);
         // compose message
         ...
         Transport.send(message);
    }

}

If you need to do this from a non-managed bean then you grab your Session instance using JNDI.  This is described in the documentation linked above.