Codeigniter private messaging module

Hi! I am working on a private project / website which has been implemented using PHP/Codeigniter, MySQL and Bootstrap CSS/JS. The site has not gone live yet as certain features are still outstanding for a beta phase. One of these features is a private messaging module/component. This module should be a simple module using which users could send private messages to each other, similar to the facebook messages module. However, no live chat required. Roughly, functional requirements would be as follows: - View inbox (display messages, sender, sent date, subject, read or unread, sort by received date) - View message (detailed view) - Send new message - Reply to message - View sent messages (outbox) - View sent message (individual message) - Send an email notification as soon as a new private message has been received - Delete a message from inbox - Delete a message from outbox - Auto-delete messages older than X days - Clean and easy-to-use interface NOT required: - Send a message to multiple recipients