Question about Outlook Express

new to outlook & macs - double whammy - and I already hate them both. one of the biggest pia's is this annoying property of bringing up all e-mail address that I HAVE REPLIED TO when I'm trying to address an e-mail. I can delete the ones with the x beside them, but many say 'work' and I cannot delete them. Most of these are not in my address book, and I can't find anywhere to change this annoying habit. Several of the searches seem to reflect a number of other people with this same request, but no one seems to have a solution.