It may be possible to send html emails from your mail client but this is not something I'm familiar with. How I usually send this type of email is by creating a page in the site and applying Universal Email to the page. You can then choose the html page you have crafted as the body of the message.
Getting the message sent to the rite people is another part of this. If you apply UE to a page that has a form in it, and the form has an input for you to enter the email address you can use the lightning bolt icon in the Universal Email server behavior for the to address to select the text input from your form. This way the email will be sent to the email address that you enter into the form. It would be a good idea to make sure this page is secure so that your page is not used as a spamming tool.
Please post back with your thoughts on this and I will try to get you headed in the right direction.