Are HTML emails more likely to be filtered in MS Outlook than plain text emails?

Answer: Outlook 2003 will no longer automatically display images in HTML email and the new Junk Mail filter, which is enabled by default, also features adaptive filtering technology. Beyond content and other factors, one of the key components of ISP filtering is incorrectly coded HTML. In fact, an estimated 9 out of 10 HTML emails are not W3C HTML compliant, which can cause rendering as well as delivery issues, particularly at MSN and Hotmail. If you use HTML in your messages, make sure your code is error-free and follows W3C HTML guidelines. Use the HTML validator in your email application or third-party validator such as The W3C Markup Validation Service.