Will your emails come in the form of ads, newsletters, deals and specials, company announcements and press releases, or discussion lists? I think the best way to present material in the BODY of the email is to make it short and sweet.
You want to lead the reader somewhere else other than the email. Don't boggle it down with tons and tons of info. Simply right something catchy that email list will show your reader where to click "Check out Lesson #1" of the eCourse they just signed up for. Then, in each email following, you can do the same. They will get used to your email style and won't delete them. The link that you give them to click on should send them to a page containing the eCourse lesson, free eBook download, newsletter in HTML format, or any other sort of offer they opted-in for.
The BODY of your email SHOULD NOT contain gobs and gobs of text. Think about it - do you ever read all of that crap when you receive an email from someone other than your friends or trusted individuals? I know I don't. Think about this...if you tried to send a message to a random list that you just bought, what would you say?