The webninja back orders module allows customers to keep an eye on products they've ordered that have gone on back order once their order has landed in your accounting system.
Once the item is back in stock - the product will be removed from the online list of back ordered items.
PLEASE NOTE: all processes related to the handling of backorders, stock management etc. will need to be handled via your existing business processes and updated in your accounting package.
Any proactive follow-up you wish to provide to your customers to notify them of the status of their back ordered products once fulfilled will need to be managed either directly from within your accounting, or via external means outside the website.
You CAN edit the order via the back-end CMS and put notes on the order via the order status update options. Just make sure to tick the box to notify the customer.
If you tick the 2nd box to Append Comments - that will also add your note onto the order's details where the customer can view their orders via the "My Account" section of the website.
Here's one possible example of how you could do that: