set DNS in email

Hi,

I want to track the emails which are sent from my portal site.

I want delivery notification for each email sent.

I have heard about the Delivery Status Notification(DNS) which needs to be set while sending email, but I couldn't find any solution of integrating using codeigniter mail function.
How should I use it.

If any other method that can track send emails, please provide me the step by step process.

Thanks.