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

 MAIL$_MESSAGE_FILE_CTX

    MAIL$_MESSAGE_FILE_CTX specifies the mail file context received
    from MAIL$MAILFILE_BEGIN to be passed to the message routines.
    The buffer address field of the item descriptor points to a
    longword that contains mail file context information.

    The item code MAIL$_MESSAGE_FILE_CTX 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.