Since Microsoft decided to set Email Marketing back a few years by using Word's rendering engine , I see a fitting simple yet unorthodox kick in the hiney to them is in order.
If you have ever worked your tail off to optimize your email message only to test it in Outlook 2007 (which for a split second before the preview kicks in gives you a nice false sense of hope) and watch it fall apart then here is a quick and simple solution that will work almost 100% of the time when spacer.gif’s are involved.
Get ready for this solution because if you blink, you may miss it. Rename your spacer.gif to spcer2.gif (or another file that doesn’t exist.) I know that it’s completely unorthodox but it works. I even tested it using Spam Assassin and it doesn’t change anything by having a few images that point to a preverbal black hole in Cyberspace. If the message has a colored background, you may see a slim white line at the bottom of your message that may need to be tweaked a little bit, however if the background is white you will never notice it.