VMS Help MAIL Routines, MAIL$MESSAGE_DELETE, Input Item Codes  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 MAIL$_MESSAGE_ID

    MAIL$_MESSAGE_ID specifies the message identification number of
    the message on which the operation is to be performed. The buffer
    address field points to a longword that contains the message
    identification number.

    The item code MAIL$_MESSAGE_ID is required.

 out_item_list

    OpenVMS usage:itmlst_3
    type:         longword
    access:       write only
    mechanism:    by reference
    Item list specifying the information you want the routine to
    return. The out_item_list argument is the address of a list of
    item descriptors, each of which describes an item of information.
    The list of item descriptors is terminated by longword value of
    0.