Rav Moshe Shternbuch: Store Delivered Mishloach Manos
A Rav paskened that you are not yotzei Mishloach Manos if you order it from a store that delivers it to the recipient's house. The reason is that since the sender did not make a kinyan it does not really belong to him rather it belongs to the store owner. In order to be yotzei the store owner must give it to a third party to be koneh on behalf of the sender and then deliver it.
Rav Moshe Shternbuch says (1:406) that this is not necessary. We find a similar halacha that one may pay the Machatzis HaShekel to the Bais HaMikdash for his friend without his friend making any kinyan in the Shekel whatsoever. Moreover he says that one of the reasons for Mishloach Manos is to increase friendship between friends. Therefore this technical detail is not critical.