HTML Email template creation

I need to create a HTML email template or if easier I need someone to create a sales introduction letter that can be sent out to many thousands of email addresses (I have the database already), but I want it to look different from a normal just same font and size thing that is the norm, I am told I need a HTML email, but I am not really sure what this is or if it is even the right thing!!! Can you help??? I know the text and have company header etc, just need it made into a nice email!