The RMA’s 695:4, psak is that if someone sends mishloach manos, even if the other is not willing to accept it, he is still performing the mitzva. Says the Chasam Sofer in the name of the Monas Halevi, the mitzva is to show love and brotherliness to each other, but not like tzadakah where the mitzva is to make sure that the other person should have. According to the Shulchan Aruch this mitzva is part of Sudas Purim such that he should share his meal with others not to be only for his stomach. Others say that this it part of Matonas Leaniyim not to shame them. if everyone gets, the poor don’t feel ashamed.