Thanks everyone in advance...
I have a user with a new device - is there any way, once folder redirection is configured on BES to get the messages dated prior to the new activation date to show on the device?

Exchange 2003/BES Professional v 4.1.4.17

Is the device already activated on BES?

Yes...

Then you'd need to remove the user's account from BES, re-add them, set up folder redirection and then do a new Enterprise Activation.

I have tried that - it still doesn't allow him to see messages that are filed in folders that are older than the activation date??

What are your pre-population settings on BES?
By default... it's 5 days or 200 message... whichever is reached first.
The maximum is 14 days or 750 messages... whichever is reached first.