I use this all the time. It's simple and it works:
NewsLetter 2.6.1 software download - Mac OS X - VersionTracker
Build it in dreamweaver like a normal page, upload it to your web server and tell newsletter where it is and who you want to send it to. Then they can forward it on and it should all stay as it is.
A couple of things - keep it really simple - any effects or movement probably won't work for everyone it reaches. I even avoid rollovers. And try and make it into one image rather than lots of little bits (I'm sure there's a technical term for this), so that the email software can't break it up. I use HTML 3.2 as well - seems to work better.
That's how I do it, I'm sure the techy people will tell me I'm going wrong in some way, but it works, and the clients are happy.