I am creating an HTML email to be sent to a user. If there is a valid email address to within an HTML email, Outlook will render it (normally helpfully) as a mailto: link.
As far as i know there is no way to do it, but you could try writing the email in a way that outlook does not recognize (i.e. try replacing the @ by it's unicode representation).
I'm no outlook expert and i never had this particular problem so i would be interested in an easier way, too.