Diane Poremsky [MVP] wrote:

you can also open it in IE and copy and paste the page into the email
message.

I wasn't aware that Outlook had a source or direct HTML edit mode?
Pasting HTML code (which is just text) into an e-mail message might
still not get the wanted result. Wouldn't it be more correct to edit
the .html file until it looks how you want in a web browser and then use
that web browser's Send Page By E-mail function? Of course, not
everything you can display in a web browser will be properly displayed
within an e-mail client that support HTML formatted e-mails. E-mail
clients are not web browsers and, for example, the default Restricted
Sites security zone used by Outlook will not run scripts, AX controls,
etc.