In Outlook (or at least older versions) there is an option to insert HTML code. So, click to write a new email message, copy the HTML code of the email (that is, the whole code for that page), click whatever button it is that allows you to insert your HTML (I don't use Outlook), and then send. If you are using the latest Outlook (2010 and even 2007?) you may not have this option any more (I vaguely remember being told it's not there any more, because they've stupidly switched to using Word integration instead). You may be able to paste your code into Word in some kind of HTML view and then suck it into Outlook, but I feel truly dirty saying that.
Another option (at least on a Mac—I'm not sure about PC) is open your email template in Safari and then go to File > Mail Contents of this Page, and it will open your mail client with the HTML email all ready to sent.
Thirdly, you can download Thunderbird, a free email client made by Mozilla (the Firefox folks) and that has a nice option to insert HTML, so that's your most reliable option.
Mehopes that helpeth.