Function: metamail-interpret-body

Interpret a body part of a MIME message in current buffer.
Optional argument VIEWMODE specifies the value of the
EMACS_VIEW_MODE environment variable (defaulted to 1).
Optional argument NODISPLAY non-nil means buffer is not
redisplayed as output is inserted.
Its header part is not interpreted at all.

(fn &optional VIEWMODE NODISPLAY)