Outlook Rules

We’re running Exchange 5.5 with SP2 and we’re having problems getting Outlook to forward messages to a Public Folder. We cannot get it to work as a server side rule. We have to leave a copy of Outlook running for it to move the messages. If we have it just forward the email to an address, it’ll work fine, but we cannot get it to copy the messages to a Public Folder without having it opened.