There are no such things as Outlook mail accounts (in the context of your question anyway). Your mail account is on a server where Outlook fetches mail from.
The better way to set up mail forwarding is on the server. If you have some sort of a web interface or a shell account, then you may be able to set the forward address yourself. Otherwise, talk to the mail server administrator.
You can set up mail filtering rules in Outlook too, which say that whenever Outlook receives a new message, it will send it so somewhere else. This approach is very bad though, since you would have to have your Outlook running 24/7 to keep the forwarding ability.