I know it's not timely, but this is a question I had thought about this past Purim. I already have some developed ideas, but I'm interested in hearing the oilam's thoughts. And the same question could be asked by a kinyan sudar/chalipin.
The Aruch Hashulchan 695:16 says if you send Shaloch Manos to someone and their not home, even if someone else accepted it for them, it doesn’t work. The reason is because it must be given into his hands. He then adds, that if he knows about it that’s also good. So obviously the kinyan is not the point but rather the increased friendships (according to this shita)
שהרי כתיב "משלוח מנות איש לרעהו", ובעינן שיבא ליד רעהו, שעל כל פנים ידע מזה