Is it possible to create a mailbox in Minecraft?

Solution 1:

Yes - the traditional apprach is to leave a mailbox - some container, like a barrel, maybe decorated to resemble a fancy mailbox, in front of your base, with a book&quill inside. Anyone can pick the book and leave you a message inside - or deliver some goods and leave them in the mailbox alongside the message.

More technically inclined players will add redstone contraptions that indicate the mailbox was used, and some even create an elaborate underground railway network, alongside with fancy routing mechanisms, to deliver the mail directly to the recipient's base using a minecarts with chest.

Solution 2:

You could make a Book and Quill with a Book, an Ink Sac and a Feather, and write the message in that. Then place a chest outside their house (leaving the book inside) and optionally adding a sign to the chest calling it a mailbox.

Solution 3:

To elaborate on some of the other ideas presented here, you could make use of Hoppers to prevent users from retracting their own (or others') books once delivered.

Users would then simply have to drop (or insert) their book - or other item - into the hopper, and have it be chained along into a chest somewhere else.

While this setup takes a significantly higher amount of resources than some of the others, it has its benefits.

You could also use hoppers connected to an outside chest to automatically transport the items out of it and move them elsewhere.