Format: EXTRACT/ATTACHMENT=attachment-number [filename]

    NOTE: The /ATTACHMENT qualifier is required with EXTRACT.
    This qualifier specifies the number of the attachment as
    displayed by the LIST command. In a single part message,
    no attachment number is displayed. For this case specify
    attachment number one.

    EXTRACT extracts the specified attachment to a file in its
    native file format or in another format specified by the /FDL
    qualifier.  By default, the attachment is written to a file in
    the default directory, using the name specified by the
    Content-Disposition header of the attachment. If no file name
    is provided, the program prompts for one. A file name can be
    specified in the command to override the value of the
    Content-Disposition header.