Vendor Drop Ship Email out

How would i get only purchase orders to be sent to the vendor?

We are closeout excess inventory liquidators for Global Industries( Vendor)(they sell office furniture) Some items are drop ship and some items we sell in our store and the items are either delivered by us or taken out of the store immediately by the customer.

I do not want Global Industries(vendor) to be sent an email every time we sell something in our store. I only want them to be sent an email when a purchase order is created for the drop ship only items.

I hope that makes sense, and you can help me out.