When you submit a letter here you are safe, anonymous, I don't even require your name or email. You don't have to worry about backlash from spilling a secret, confessing a secret crush, complaining about work, friends, an ex, school, you name it. Even passive aggressive letters can make you feel better!
So if there is something you wanted to say but never did; maybe you were scared of the backlash, or they are no longer alive. Now you can, it helps to get the emotions out, to write it down- even if it goes unsent. You can submit your letter using the from here and get it off your chest. And if you really want to be sure the person the letter is to reads the letter, I can snail-mail it anonymously for you too.