1    /BUFFER_SIZE

       /BUFFER_SIZE=n

    Specifies the number of bytes of system dynamic memory that can
    be used to buffer messages sent to the mailbox. If you do not
    specify /BUFFER_SIZE or specify it as 0, the operating system
    provides a default value from the DEFMBXBUFQUO system parameter.

2    /LOG

       /LOG
       /NOLOG (default)

    Displays the name of the new mailbox when it is created.

3    /MESSAGE_SIZE

       /MESSAGE_SIZE=n

    Specifies the maximum size (in bytes) of a message that can be
    sent to the mailbox. The maximum value is 65535. If you do not
    specify /MESSAGE_SIZE or specify the value as 0, the operating
    system provides a default value from the DEFMBXMXMSG system
    parameter.

4    /PERMANENT

    Specifies that the mailbox is to be permanent. By default,
    mailboxes are temporary.

5    /PROTECTION

       /PROTECTION=(ownership[:access][,...])

    Specifies protection for the mailbox.

    o  Specify the ownership parameter as system (S),  owner (O),
       group (G),  or world (W).

    o  Specify the access parameter as read (R),  write (W), logical
       I/O (L),  or physical I/O (P).

    If no protection is specified, the mailbox template is used.

    For more information about specifying protection codes, see the
    VSI OpenVMS Guide to System Security.

6    /TEMPORARY

       /TEMPORARY (default)

    Specifies that the mailbox is temporary. By default, mailboxes
    are temporary unless you specify /PERMANENT.