Here are a few things you cant do with email:
- Include a section with styles. Apple Mail.app supports it, but Gmail and Hotmail do not, so it's a no-no. Hotmail will support a style section in the body but Gmail still doesn't.
- Link to an external stylesheet. Not many email clients support this, best to just forget it.
- Background-image / Background-position. Gmail is also the culprit on this one.
- Clear your floats. Gmail again.
- Margin. Yep, seriously, Hotmail ignores margins. Basically any CSS positioning at all doesn't work.
- Font-anything. Chances are Eudora will ignore anything you try to declare with fonts.
Source: http://css-tricks.com/using-css-in-html-emails-the-real-story/
Mailchimp has email templates you can use - here
A few more resources that should help you