How to get HTML to render properly in Email clients?

or at least Thunderbird, and Outlook

[benlieb]

I've made some HTML-based email "newsletters" but can't seem to get consistency across mail clients.

I've noticed that most of the spammers never use background images, or rely on CSS. Is this recommended practice?

Are there any (other) tricks people have come up with?

[NewSkool]

e-mail = text only

[Mr Bo Jangles]

CSS isn't recommended for HTML e-mail.
Also, use tables for positioning.
Look at the source of some of the HTML e-mails and newsletters you get from the bigger companies, and see how their experts have done it.