My response to someone asking if they should continue to send gifts, cards etc, to their alienated son.
"Send him all those things, whether they come back or not.
If he accepts them with or without thanks, he accepts you to some extent.
If he rejects them, he still knows you tried (and I don't believe that children who reject gifts from parents are doing so entirely of their own free will).
If you don't, he'll think "She didn't send me anything. Dad was right. She doesn't care about me".
If may seem like you can't win, but it's not the gifts that matter here - it's that you're sending them.
Another thought has just come to me - when my mother gave me gifts to open on my birthday at my male parent's house (my birthday is in the summer so we'd spend a week or two with him), he liked to watch me open them and sat like a vulture waiting for a reponse or comparison with what he had given me. He liked to mock things she said and did and didn't exclude birthday presents, but even if he said nothing about her gifts, I was tense and stressed WAITING for him to say something horrible which would inevitably spoil the day. I can recall the dread right now as I type. And if I liked what she bought me ... I'd be in for an anti-mum earbashing at some point, whether it was about the gifts or not. He'd find some way of spoiling her efforts.