Messenger Addon

The Messenger addon is a tool for allowing players to message other players even when they are offline. 

Commands:
/mail <target user> < message > //Attempts to send the message to the user. If they are online, they receive the message. If they are offline, they will receive all their messages when they come online. Messages are immediately deleted after reading to save on space.
/mail undo //If the previous message has not been deleted (aka viewed) it will be deleted and all traces of it destroyed. You can type this command multiple times to keep removing previous messages.
/mail read //Read all the mail that you have sent (that has not been read by their receiver)

This addon is persistent meaning if the server restarts, all the messages will still get to their destination some time. Unless the server happens to restart in the middle of a save operation (I think this will be rare but it will end up wiping all messages previously saved).

This is disable able via configs.