Your best solution for the user requirements is to use the blackberry professional software (BPS). Redirector only forwards mail and does not sync mail. BPS is very cheaps compared to BES and will handle all emails, including attachments. The redirector just has too many limitations and is not really that configurable, plus you always have to have an active outlook client connection to make it work.
The Blackberry Internet Service (BIS) could be a solution, you would set it up to work with OWA and create the outlook rules for those emails and put them in subfolders. Problem is BIS does not handle subfolders.
BPS gives you a lot of other controls and advantages, such as wireless sync for those components that your user now with Desktop Manager needs to sync with a usb cable.
