My child sent emails to every alumni interviewer when she was applying to college last year.
When she interviewed with college faculty for scholarships she sent them all paper thank you notes.
Also, she has BOXES of thank you notes/note cards and a pack of stamps at school. She has been in the habit of giving/sending a paper thank you note since middle school. When I see thank you notes on sale, I buy the nicest and most deeply discounted boxes. It amazes me how something so small makes her stand out so much, and it takes, at most, 10 minutes of her time.