Basically it sounds as though you want to send an html newsletter. I'm not quite suire what you mean though by "the newsletter is open when they receive it". If you are referring to images being automically downloaded when they open the email there is no way to make this happen for security reasons unless the user explicity allows it.
Personally speaking designing for emails is a lot different than designing for web users. First off, you stay away from divs and stick to a table based layout. Second, background-images are also no good because Outlook does not allow them and if you are emailing business customers, it won't look good.
My personal suggestion to you would be to look into email services like those offered by Mailchimp (http://www.mailchimp.com) or Constant Contact (http://www.constantcontact.com). Mailchimp tends to be a little more advanced, but it gives you more freedom to import html documents that you make in Dreamweaver and they also have a plugin (I have not tested it yet with CS5, but it works in CS4).
I'm really happy with Campaign Monitor which I've just used to send my first newsletter. Really simple to upload hml and they have a v cool testing report so you can see what the email looks like on all browsers.