That's all right, I constantly contact my rep and US Senators and all I get is a form letter saying thank you.......LOL!
I mailed him a card, a few years ago. Some time went by and pretty soon, a response came back to me. Of course it wasn’t from him personally, but AT LEAST it was a response. I believe his staff members (or somebody) keep track of how much mail he receives. But it is that way for any president.