The best way to send an HTML email through Entourage is via MS Word. Entourage’s HTML editing engine is very basic. It is impossible to make text a link, ie you can’t make Telos Studios a link to http://www.telosstudios.com. It will automatically make URLs in text links, which is not adequate.

After you’ve created your email message in Word, goto File > Send To > Mail Recipient (as HTML) … That should do it. This method will also allow you to send tables, images, and other more complex HTML.