Why can't I set up a printed footer on an HTML mail message?
Although Outlook lets you use File, Page Setup to set up headers and footers for messages printed with the Memo Style, those settings don't apply to HTML mail messages. For HTML-format messages, Outlook turns printing over to Microsoft Internet Explorer (IE), whose components perform the message's HTML rendering.
However, the delegation of control to IE seems to be incomplete—at least in IE 6.0, in which I did my testing. Even if you change the footer by choosing File, Page Setup to include both the date and the time, the HTML mail message printout includes only the date. I don't know any way around this bug, except to save the message as an .htm file and open it directly in IE for printing.
By the way, because Outlook, Outlook Express, and IE share the same HTML rendering engine, you don't need three different HTML engines running on your machine at the same time. However, you need to keep IE updated with the latest patches if you want to be safe from viruses that can take advantage of vulnerabilities in HTML mail messages.