Agreed with goldfries & @meno statement. And that is what i used to with my own postage deal. Wrap up all the whole box with few layer of paper and seal it with as much tape as i could.

And usually I'll snap picture of the parcel before ship out, the shipping receipt and upload to buyer so that can have a copy of the shipping receipt and a rough idea how the parcel will going to be look like. Incase anything thing, there are still are reference that can refer to.