/ZONE[=domain]
       /NOZONE[=domain]

    Optional. Default: /NOZONE (no gateway searching).

    Domain for your environment (probably a superset of your local
    domain).

    Mail sent to another network must be sent to this gateway.

    With no value, /ZONE defaults to one level higher than your local
    domain.

    For example, if your local domain is a.b.com, the default value
    of /ZONE is b.com because TCP/IP Services has been started; this
    assumes that the domain is known.

    Mail for delivery outside of your zone is sent to its destination
    by the alternate gateway (see the /GATEWAY qualifier).