You can't really do that...at least not as simply as your question puts it. You can save the InDesign document as HTML, but the type of email "blast" you have in mind isn't "any" HTML. Email clients don't render HTML pages the same way web browsers do, and deployment and tracking of such emails is usually handled by specialized, 3rd-party services. Do a bit of reaserch into these services, (example: 'Constant Contact'), and you'll start to see that you can't really do email marketing with just an email client. You'd have a much easier time if you just settle for attaching the flyer as a PDF.
Thank you so much John. This answered my question. I do have a constant contact account. Am I able to bring my specially designed flyer into CC or do I have to use one of their templates; do you know?
Any how, I won't take up more of our time. Thanks again and have a happy week.
I don't have first-hand experience with Constant Contact, but if its online interface offers HTML editing, you can save your flyer as HTML/CSS, then copy/paste the HTML code and then add inline styling. It's not likely you'll get one-to-one results, but it might serve as a starting point you can work with.