Does Ben Platt respond to fan mail?

Has anyone tried sending him anything and has he responded?

Why not just send your letter? There could be any number of reasons why an actor does or does not respond. An actor who typically responds may just all of a sudden get inundated with fanmail and not have time, or he/she may have lots of time and respond to all. If someone here posts "no," it doesn't mean he never responds, and you'll miss an opportunity to write him.

If your goal in writing him is specifically to generate a response, then I can see the point of your question. If you simply want to write him and say how much you enjoyed his performance, or how some mannerism or character trait of his resonated within you, then send away and know it's a 99.9% guarantee he'll receive and read the letter.