Mailbox

In every game, a red mailbox can be found outside the player's house. It is where Pete puts letters addressed to the player. When a letter arrives, a blue signal with a small blinking letter will appear on the right-top of the mailbox and will make a faint beeping sound when the player walks near it. In, a full mailbox will be indicated by faster beeping, and the mailbox will shake rapidly. Only the owner of the house can open the mailbox.

In
In, There is a Red Mailbox with "POST" written on it. If a player attempts to mail something to a player whose mailbox is currently full, Pelly or Phyllis will tell the player that the other player's mailbox is full, and to ask them to clear out their mailbox. If Phyllis is there, she will say "I can't take it, and I don't want it!" due to her grumpy nature. If the player is in the same acre as the houses and the clock turns to 9:00 AM or 5:00 PM, Pete will fly down and deliver any sent mail. If there is nothing in the Post Office when the clock changes, there will be no mail to deliver, and thus Pete will not show up.

In
In, different forms of mailboxes are available to buy from Tom Nook at his new shop, Nook's Homes, in a variety of different styles and colors. New mailboxes cost 3,600 bells. There are 21 different styles to choose from. Each style has a theme, such as Fairy Tale, Antique, or Trendy. When a player's mailbox is full, it will shake violently, beep very loudly, and the flap will snap open and shut. It will shake faster and faster the closer a player walks to it. Pete the mail pelican will also tell the other players about it when they exit their house, asking them to tell their friend to clear their full mailbox. After giving the player the message, Pete will wander around for a while and can still be spoken to.

In
In, the player has a mailbox from which they can collect rewards from completing quests.

Appearances in other games
In Super Smash Bros. Brawl, one of the trophies available features a male player, and next to him is a mailbox which holds unread mail, shown by the blue sign on the mailbox.

Trivia

 * is the only game where a player can open their mailbox even if there's nothing in it.