unless ``--part=N`` is used to select a specific part or
``--include-html`` is used to include all "text/html" parts, no
part with content type "text/html" is included in the output.
unless ``--part=N`` is used to select a specific part or
``--include-html`` is used to include all "text/html" parts, no
part with content type "text/html" is included in the output.