I'm sorry, that last reply was sent by me in error.
To answer your question, I only have Outlook 2003, so what I say might not
apply to you; but in my version, I did some Search research, and I found this
(easily)
With the message open, on the Edit menu, click Edit Message.
On the Format menu, click the format you want to use (Plain Text, HTML, or
Rich Text).
Note If Word is not your e-mail editor, you can convert HTML or RTF to
plain text, and you can convert plain text to RTF or HTML. However, you
cannot convert HTML to RTF or RTF to HTML.
this is for When reading a plain text or HTML message
(I just copied right from the help topic)