How can i find out about being a military penpal?

i want to become a penpal with a soldier overseas, where i can write handwritten letters to a soldier and they write back handwritten letters through the mail. are there any secific websites where i can register or something and get their direct adresses?
I remember when I was in Iraq (2008) one of my fellow marines recieved letters from a penpal. I want to say that she was with a thing called soldiers angels? Try looking it up. She said that she signed up an you can pick through a list of deployed service members (any branch) and basically 'adopt' them. It's a good thing, he loved the support, who doesn't :) Thank you for wanting to help.