In KinzPost, you can send letters or packages with items inside to people on your friends list. There is a fee for this service. In the letters, you can put stickers, change the paper, and add various predetermined messages. In packages, you can send up to 3 items, and you are charged KinzCash for everything you send. You used to be able to send eCards based on Webkinz World.
Here is you what you see in your mail sometimes: