Recently I had to debug an HTML email issue where the layout was not showing as expected. I soon found and used Premailer which was a huge help. Simply point the tool to either a URL or copy and paste in the code you would like to use and it will do the following:

• Remove classes
• Remove unused IDs
• Remove comments
• CSS styles are converted to inline style attributes
• Relative paths are converted to absolute paths
• CSS properties are checked against e-mail client capabilities
• A plain text version is created

After you submit your URL or code, it will give you the HTML and plain text versions to download as well as show you any warnings about remaining styles/code which if you know your audience – you can then use to further make decisions about styling/coding your newsletter.