outlook 2000 out of office

I work for a company which has a Lan. I work from home and use different e-mail address but mostly yahoo and AOL when I send an e-mail to the office and the other user is not in but has there outlook 2000 out office on, I do not get a out of office reply from user? I found out it works internaly but not externaly, is it something I need to change at home or is it the office LAN?