How can I redirect mail sent to a particular mailbox to an external address?
Outlook 2000 has the ability, in the Rules Wizard, to redirect mail. You’ll find it under the allowable actions when you create a new rule to check incoming messages.
Another option would be to create a Custom Recipient for the external address, then configure that Custom Recipient as an Alternate Recipient for the mailbox in question. That’s in the Exchange Administrator -> Mailbox Properties (for the mailbox you want to redirect) -> Delivery Options.