Penguin Mail was first introduced on July 14, 2008. It was one of the many features that were involved with testing in the Club Penguin Improvement Project. Penguin Mail allowed players to save and delete postcards, send postcards to buddies even when they were offline, and receive postcards from puffles when they are hungry. Before Penguin Mail was launched, players could not do this. When Penguin Mail was launched, all players were given a postcard that gave a free Blue Mail Bag. There was once a trash button. However, it was permanently changed during the Earth Day 2010 so that it would be recycled. The Penguin Mail postcard updated every month or so and it cost 10 coins to send a postcard.
- There was a glitch that let you stand in pathways by using Penguin Mail. Penguins could do it by clicking the path, opening Penguin Mail, waiting a few seconds and then closing Penguin Mail to see their penguin in the pathway.
- The Blue Mail Bag, Candy Cane Hat, Holiday Toque, and the Springy Santa Hat could be obtained through Penguin Mail.
- You could only have up to 99 Postcards as a member. Non-members could only have up to 50 postcards.
- There was a story that referenced Penguin Mail. It showed how a Green Puffle and a Puffle Cannon was used to increase the speed of delivery.
- Before the Earth Day 2010, when you deleted a postcard, you would click "Trash!". From Earth Day 2010 onwards, you would click "Recycle!" when deleting a postcard.