This is a mod for Minetest.
Its Add moreinventories:
backpack, password chest, player chest, digable chest and a post system.

crafts:
*******

|W| |W|
|W|C|W| = Backpack
|W| |W|
W = Wood
C = Digable chest

|C|C|C|
|C| |C| = Password chest
|C|C|C|
C = Chest

|C|C| = Digable chest
C = Chest

|C| = Player chest
C = Password chest

backpack:
*********
left-click to open.

password chest:
***************
enter name and password to connect/create to network.
if name is new a new network is createt.
if name is old you connect to exist network.
if password is incorrect you cannot connect to network.
All password chest with the same name and correct password are connected.

digable chest:
**************
Is a chest you can dig even if full.
If you dig inventory keeps.

Player chest:
*************
Is a chest for you.
If you open any player chest, you see the same inventory.
Is save, because only you can access to inventory.

Post:
*****
You can access your inbox use /inbox.
You can only take items from your inbox.

You can send items to friends(on the same server) use /send <name>.
<name> is the name of your friend.
If you have post you see a message on chat.