In Outlook, your emails can be formatted in HTML OR with Word.
HTML has some serious holes in it and unless the firewall grabs it, there can be active content within that HTML.
My mom uses Hotmail (please spare the laughter), am I going to be wiping her computer clean in the near future?
Not really. Using Word as an e-mail editor formats your mail in HTML, RTF or plain text. There is no "Word" format.