It is essential to be able to email customers from the processed orders screen. If a customer emails and wants to know how to cancel or send an order back this is absolutely crucial. I cannot believe there is no facility for this.

I have been asking for this for the last 5 years and have no idea why this is bot a basic function

Doesnt the cancellation of the order depend on the channel it was ordered through and payment method used? ie some might use ebay / paypal / resolution cases others might use worldpay etc,