Use the DIRECTORY command to list any messages which you've sent
    but which have not yet been delivered. The optional type argument
    can be used to restrict the listing to certain types of messages
    such as messages sent to the Internet or other TCP/IP connected
    machines such as UNIX workstations, cc:Mail users, FAX machines,
    etc. A complete list of the available types are shown below. You
    can also use the ? key to obtain a listing of the available types
    as shown in the examples below.

    Type         Message Types Listed

    all_in_1     Messages sent to ALL-IN-1 users
    bitnet       Messages set to BITNET users
    ccmail       Messages sent to Lotus cc:Mail users
    decnet       Messages sent to DECnet users
    fax          Messages sent as FAXes via PMDF-FAX
    groupwise    Messages to GroupWise Office users
    internet     Messages sent to Internet users
    local        Messages sent to local VMS MAIL users
    lotus_notes  Messages sent to Lotus Notes users
    mailbus_400  Messages sent to MAILbus 400 users
    mailworks    Messages sent to MailWorks users
    message_     Messages sent to Message Router users
    router
    microsoft_   Messages sent to Microsoft Mail users
    mail
    netdata      Messages sent to Netdata (PROFS) users
    novell_mhs   Messages sent to Novell MHS users
    ovvm         Messages sent to OV/VM (PROFS) users
    pager        Messages sent to personal pagers
    popstore     Messages sent to popstore users
    snads        Messages sent to SNADS users
    tcpip        Messages sent to TCP/IP users
    teamlinks    Messages sent to TeamLinks users
    uucp         Messages sent to UUCP users
    wordperfect  Messages sent to WordPerfect Office users
    x400         Messages sent to X.400 users

    In the directory listing, each message is assigned a message
    identification number, or "message id" for short. The message id
    appears in the leftmost column. These identification numbers can
    be used with the READ, RETURN, and EDIT_FAX commands to identify
    which messages to read, return, or edit.

    It is important to note that when you send a message to more
    than one recipient, the message might split into multiple message
    copies. Consequently, the same message might appear multiple
    times as being queued to different networks (or possibly even for
    the same network). Such would be the case for a message sent both
    to local users and remote users.