[otrs] how to send email to notify ticket status change

I just recently started using the OTRS system. Most of the features are great but one thing I haven't been able to do is to send an email to the customers saying there is a change in their ticket status. For example, once a customer logs in through the customer interface and sends a ticket if we add a response to it or change it somehow, how can i send a notification email to the customer? thanks a bunch in advance