Ah, one little detail buried in the posts -- it's an E-mail.
Generally speaking, R-mails are VERY different from writing web pages, and that's what's biting you. As a rule of thumb, it's a bad idea to even MAKE styled e-mails as a lot of hosts use it as a spam filter. I know my setups all do because there is no legitimate excuse for someone sending me a legitimate e-mail to send one done with HTML.
That said, mail clients on the whole choke badly on HTML e-mails because their rendering engines usually haven't been updated since 1996 -- That's NOT a joke. On the whole they support HTML 3.2 BARELY, and CSS support is spotty if nonexistent. AS SUCH, trying to use CSS in a HTML e-mail is NOT GOING TO WORK reliably across all the different mail clients out there.
AS SUCH, to make a working HTML e-mail you have to dial the clock back to 1997 and write nothing but HTML 3.2 without CSS, and even then you'll want to check at least FIVE mail clients (Three webmail, outlook, thunderbird) to see if it actually works how you want.
Then of course there's the other thing biting you, your tools. Now I'm not saying that using anything more complex than a flat text editor is a waste of time, and I'm not saying that you can't learn anything from Dreamweaver aside from how not to build a site... No, wait... That's EXACTLY what I'm saying.
If you REALLY have your heart set on doing this, you should be working from a flat text editor, and I'd suggest using something like Oracle VirtualBox with Windows 98 installed in it to test in Nyetscape 4 and IE 5.0 (NOT 5.5, too new). If you can get it working in both of those WITHOUT using CSS, it will work in an e-mail.
But again, I wouldn't be wasting my time on that crap in the first place as again, I block them by default as do a lot of other people. HTML in e-mail was a dumb idea at the start, and it's not really viable given that all the mail clients (other than the now defunct Opera 12/earlier) haven't bothered updating their rendering engines in what is rapidly closing on two decades.