Author: Peter Koprda xkoprd00@stud.fit.vutbr.cz
$ bin/client [OPTION ...] COMMAND [ARGS]
-a <addr>, --address <addr> Server hostname or address to connect to
-p <port>, --port <port> Server port to connect to
--help, -h Show this help
register <username> <password>
login <username> <password>
list
send <recipient> <subject> <body>
fetch <id>
logout