When I sell stuff, which is not very often these days, I always send out an e-mail to the buyer thanking them for their purchase and then, amongst other things, I mention that I don't leave feedback until the buyer lets me know that their item has been received in good condition and that it is just what they wanted, adding that they can let me know by either sending me an e-mail or leaving feedback. I will then be delighted to leave Pos feedback for them.