Penguin Mail was first introduced on July 14, 2008 as one of the many features that were involved with testing in the Club Penguin Improvement Project. Penguin Mail allowed players to send, receive, delete, save and reply to postcards from other penguins. Additionally, players could also receive postcards from their puffles when they were hungry, automated postcards to advertise parties, and monthly salaries for being a Tour Guide or Secret Agent. Postcards could be purchased and sent from the Postcard Catalog for 10 coins.
- 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.
- The story "The Day my Puffle Went On an Adventure" by Chochypop in Penguin Tales: Spring '08 references Penguin Mail.
- From Earth Day 2010 onwards, the "TRASH!" button was replaced with a"Recycle!" button.
- When Penguin Mail was launched, all players were given a postcard that contained a free Blue Mail Bag.