There should be a mail-service.xml in the deploy directory jsut for this purpose. You can bind to the JNDI name for the mail services which is java:/Mail. It binds the JavaMail Session to this name which can be used in client applications.
Just make sure that your mbean depends on mail-service so that the JNDI Name is bound by mail-service before you start using it in ur mbean.
Context initial = new InitialContext();
Session session =
msg = new MimeMessage(session);
Now you're all good to go. Just use java mail api. You'll use the transport to send it.