If HTML is selected as the email format in Outlook, then you type your message and WYSIWYG. The Outlook editor lets you format fonts, colors, backgrounds, insert pictures, etc. but not much more. If you want more advanced HTML, it's probably easier to use a full HTML editor like FrontPage (or others). With most editors you could copy and paste to your email, or with FrontPage you can just make the page and then use File, Send... If you want to work with source html then do it with a text editor, save it as an .htm file, open it with a browser and copy and paste to email.