Whitelist

If You set whitelist 1, then only players You added to corresponding whitelist can interact with You.

List of whitelists:
allowall - ultimate white list, players listed here can fully interact with You
allowtell - players listed here can talk/chat with You
allowplay - players listed here can match You 

To see who is in Your list use =list,
to add/remove player use +/-list player.
Example:
I have 3 friends SKAcz, Matejus, Wir and only with them wish interact on server.
So I will use this commands:
+allowall SKAcz
+allowall Matejus
+allowall Wir
set whitelist 1

Also i can check list like 
=allowall
-- allowall list: 3 names --
Matejus  SKAcz    Wir  

See also blacklist

