The DIRECTORY command provides a directory listing of the
    available files. The listing is returned to you as a mail
    message.

    The file-spec parameter is optional and, if omitted, defaults
    to "*". If you are unsure of what to use, omit the parameter and
    send simply the command

    DIRECTORY

    This will provide you with a list of the files and directories
    in the top-level directory of the mail server. You can then
    this information to refine your queries; e.g., investigate the
    contents of an intriguing directory,

    DIRECTORY [GAMES...]