MAIL$_MAILFILE_DELETED_BYTES

    When you specify MAIL$_MAILFILE_DELETED_BYTES, MAIL$MAILFILE_OPEN
    returns the number of deleted bytes in the specified mail file as
    a longword value.

 MAIL$_MAILFILE_INDEXED

    When you specify MAIL$_MAILFILE_INDEXED, MAIL$MAILFILE_OPEN
    returns a Boolean TRUE when you open an indexed file. The buffer
    length field points to a longword that receives the Boolean
    value.

 MAIL$_MAILFILE_RESULTSPEC

    When you specify MAIL$_MAILFILE_RESULTSPEC, MAIL$MAILFILE_OPEN
    returns the resultant mail file specification. The buffer address
    field of the item descriptor points to a buffer that receives a
    character string 0 to 255 characters long.

    Specify a value from 0 to 255 in the buffer length field of the
    item descriptor.

 MAIL$_MAILFILE_WASTEBASKET

    When you specify MAIL$_MAILFILE_WASTEBASKET, MAIL$MAILFILE_OPEN
    returns the name of the wastebasket for the specified mail file.
    The buffer address field of the item descriptor points to a
    buffer that receives a character string 0 to 255 characters long.

    Specify a value from 0 to 255 in the buffer length field of the
    item descriptor.