mmm. Iwould have to say classic bed
OMgI've got Agent S and Kiki as my villager like you Farobi
I've sent letters out everyday with gifts to my villagers since the game started. I still have all the same villagers and I have never had an item back. I don't know what's going wrong.
However, I get around four items given to me in person a day from them.
Did you wrap the items up?
They'll only send something back if you buy some wrapping paper from Nook's and wrap the present in.