mml-preview
mml-preview is an interactive compiled Lisp function in `mml.el
'.
(mml-preview &optional RAW)
Display current buffer with Gnus, in a new buffer.
If RAW, display a raw encoded MIME message.
The window layout for the preview buffer is controlled by the variables
`special-display-buffer-names', `special-display-regexps', or
`gnus-buffer-configuration' (the first match made will be used),
or the `pop-to-buffer' function.