Turn off "your order is ready to be downloaded"

Hi,

I'm using Appointments+ with Marketpress. I have all my services sent to digital products.

It's only happened once recently but when I made a test order I got an order confirmation email and then another email telling me my order was ready to be downloaded.

Obviously I dont want that second email to be sent and like I say it's only happened once recently. Can someone explain how to ensure it's not sent again in the future and under what circumstances it gets sent

Many Thanks
Kieran