One of the managers uses this feature in his outlook but would like it to work on his phone as well when replying to clients emails.

This option can be found in outlook under
-Tools
-Options (Preferances Tab)
-Choose Email Options button
-Choose Advanced E-mail Options button (on that screen you will see the option for "In folders other than the Inbox, Save replies with original message"

I'm sure this co-insides with his rules he has in his outlook for certain clients to move the mail to certain folders. But in his client when he replies to the client it puts a copy of the sent email in that folder as well.

Is this option available in BES? I took a look but couldnt see anything. He does have most of his folders for redirection set on the bes.

Can anyone point me in the proper direction?

Regards,

IMO cannot see a way to do this on BB

not possible; the function Outlook is doing is a client side function ... BES doesn't support this.