When Outlook 2003 is installed for the first time, it uses the version of IE that is installed on that particular OS as it's rendering engine. From there, if IE6 is upgraded to IE7, Outlook will still use the original version of IE (in this case IE6).
So this means Outlook 2000/2003 could use any version of IE up to 11. It all depends on which version is present on the system when Outlook is installed.
Hello,
According to this post from Email on Acid :
So this means Outlook 2000/2003 could use any version of IE up to 11. It all depends on which version is present on the system when Outlook is installed.
Here in Litmus which version is used when rendering the previews of Outlook 2000/2003?