If you wish to turn off marketplace notifications on an order-by-order basis, that is very easy. Simply navigate to your Orders,
Next, find the order that you wish to turn off the notification for and click on its Order#. This should open up the Order Details pop-up window. Here, go to Shipping (second tab at the top) and then click on More Options,
In the Other Shipping Options section, make sure that the box next to Do not notify marketplace when shipped is not checked.
Don’t forget to click on Save&Close when you’re done!