You need to send it to their username that they signed up with for in-game purposes, not the name they use on the forum, as they have the ability to make it different than their username. When you send it to their actual username it will go to that person and that person only. Make sure to type their username without quotes (ex: "wolffox" is a no-no) otherwise it will send it to another person with the forum nickname "Zombie" and not the user you're wishing to send it to.