Out of stock notification email

Hello,

Many times you will come across an item that the inventory is out of stock but in RMS it still has stock. Basically, the inventory is wrong. When inventory is wrong the customer browsing the website can place the order. The order comes into RMS and a pick ticket gets printed. When it comes to collecting the items, the clerk realizes that one item from the order is out of stock. Now when they come to process the order, they will change the quantity of that item to 0 (zero).

Here is my question, i would like that the system should automatically send an Out of Stock notification to the customer. How can this be done?

Thank you
Isaac