To send a letter, the player must first obtain some stationery, which is sold in packs of four at Tom Nook's store (or Timmy and Tommy's store in Animal Crossing: New Leaf) for 160 bells. After the stationery is obtained and then selected in the player's inventory, the player must then choose the 'Write Letter' option. After the player has selected the recipient, the letter may now be composed. In Animal Crossing, Animal Crossing: City Folk and Animal Crossing: New Leaf, each letter has six lines to write on, whereas a letter in Animal Crossing: Wild World has only four. The lines containing the writer's name and the receiver's name can also be edited, but the recipient's name cannot be removed.
Once the letter has been written, the player is then given a complete view of the letter to allow for proofreading. Once accepted, the letter then appears in the mail section of the player's inventory. From there, it can be re-addressed, deleted, re-written or have a gift attached to it. All items except fish, bugs and turnips can be sent as a gift.
Once the player is satisfied with the letter, it must then be taken to the Post Office (Animal Crossing and Animal Crossing: New Leaf) or the Town Hall (Animal Crossing: Wild World and Animal Crossing: City Folk) to be sent for delivery. In Animal Crossing, when all five letters are sent in one go (the max that the post office can hold at one time), Pete the mailman can be seen flying into the air when the player leaves the building. After he has flown off, the post office is empty and the player can again send a maximum of five letters.
Available recipients include the following:
- The player's future self at a given date and time (starting with Animal Crossing: Wild World). The player may send only one future letter per day.
- Villagers of the player's town, and, in Animal Crossing: Wild World, Animal Crossing: City Folk and Animal Crossing: New Leaf, villagers on another player's friend roster.
- Other players living in the town and, in Wild World, City Folk and New Leaf, players on the friend roster.
- Farway Museum (Animal Crossing only) - fossils must be sent there for identification.
If a letter containing significant spelling and grammar errors is sent to a villager, this may result in a complaint by the villager.
Letters are always replied to by villagers. Letters can be received from all manner of animals, some as a result of special events. Here is a list of characters that send letters to the player:
- Other players.
- Villagers - Usually in reply to a sent letter, when moving out of the town, wishing the player a happy birthday, or inviting them to a birthday party (Animal Crossing: Wild World only).
- Other towns; Villagers (while in another town) - Usually asking if the player had a good time in the other town and telling the player to visit again.
- Farway Museum (Animal Crossing only) - Returning the fossil sent, explaining what it is.
- The player's parents - Usually only the player's mother writing at the beginning of each season or for the player's birthday. The player's father writes only on Father's Day. The parents wishing the player a happy solo adventure as the mayor (Animal Crossing: New Leaf only).
- The Happy Room Academy - Every week a letter is sent to the player containing an evaluation of the player's house with a score, unless the player has told Lyle to stop sending letters (Animal Crossing: City Folk only). In Animal Crossing: New Leaf, a letter is sent along with a prize when the player reaches a certain number of points.
- The Savings Account or Automatic Bell Dispenser - A letter is sent every month notifying the player about how many bells he or she has earned in interest. A letter is also sent whenever the player reaches a set amount of bells, along with a present for reaching that amount.
- Special Characters - Usually to advertise events. For example, Jack sends a letter to the player at the start of October about Halloween, telling them to stock up on candy.
Letters have a present attached only if one is sent to the recipient.
Depending on how many lines players write a neighbor, they can give them different items in return. For example, if players give them a piece of fruit and write them a one line long letter, they will give the player a piece of fruit back. This can be any type of fruit.