Exchange 5.5 Mail Forwarding

I would like to have incoming POP mail for one of my user accounts to forward to another outside email address. I have created an exchange mailbox to receive the POP mail, and custom recipient for the outside email address. I can send to the exchange mailbox internally and it will forward to the custom recipient address. But I would like the mailbox to autoforward to the custom recipient after connecting to the POP server. Any suggestions on how to forward these incoming messages to the custom recipient?