When building HTML emails forget everything you know about modern, best practice HTML/CSS. Support for these is very limited and has taken a step backwards with Outlook 2007 (http://www.campaignmonitor.com/blog/archives/2007/01/the_truth_behind_the_outlook_2.html)
- Use tables for any kind of complex layout.
- Don’t use CSS positoning – Outlook 2007 doesn’t support it and emails can have text appended to the bottom (e.g. by email filtering software) that can overwrite what you’ve put in the email.
- Use old-style presentational tags (e.g. font, b, align) or inline styles. Webmail tends to strip out any <style> tags and inline styles override any global styles that Hotmail or Gmail might have
- Background images should be avoided or take into account that lots of people won’t see them
- Test in as many email clients as you can
- You can get round all this by using one big image, but this is more likely to be flagged as spam by filters
- Remember if the email is going to consumers, they are more likely to have Outlook Express than Outlook that we use