Not all attachments (content-type/subtypes, such as .DOC and .XLS),
    can be displayed with the OpenVMS MIME utility. OpenVMS MIME
    displays only the attachments that have been defined and have a
    native OpenVMS viewer application installed and associated with
    that defined content-type/subtype.

    Example OpenVMS native viewer applications include NETSCAPE to
    display .HTML and .HTM attachments, and Freeware X-VIEW application
    to display image types .JPG, .GIF, and .JPEG subtypes.

    Also note that foreign commands must be defined for invoking these
    native viewer application images. This is so OpenVMS MIME can pass
    a filename (string) representing the attachment to the viewer
    application, for example:

 	NETSCAPE :== $ SYS$MANAGER:NETSCAPE-EXPORT-ALPHA-V303C4R-JAVA-GOLD.EXE

 	XV == "$ SYS$LIBRARY:XV.EXE"

    Content-types/subtypes are defined internally by OpenVMS MIME and
    in optional MIME$MAILCAP.DAT files.

    The MIME command SHOW CONTENT lists the content types of files
    that can be displayed with the READ command. Other optional types
    are defined in MIME$MAILCAP.DAT file.

 	MIME> SHOW CONTENT_TYPE

    See the READ command and SHOW CONTENT MIME$MAILCAP.DAT command for
    more information and its security implications.