
third-party [on|off]                                  Default: on

        Display or set the third-party flag.  When set to 'on', the
        mailbox will handle third-party messages.  Note that if the
        'mbox header off' command is executed, the third-party flag
        is automatically turned 'off'.

        A third-party message is a message whose To: address contains
        an '@', '%', or '!' character, or is not addressed to "sysop"
        nor the <hostname> call nor is a public area name.
