Thanks for answering my post, jpaf! We do not have a Blackberry Enterprise server and no longer use redirector. We use our service provider's server, so I believe the correct answer is BIS.
If by "mail client" you are asking if we have received the old email through Outlook as well as on our Blackberrys, the answer is no. The mail only shows up on the Blackberrys.
I'm really not sure where the email is being moved back from since it's been a year since I originally got it, but I've been wondering about the same thing.
I BELIEVE that I have only had this problem with other people I work with. Again, we all use the same service provider, but not BB Enterprise Server.
Thanks so much for any other insights you might have. I would find any ideas of yours helpful. Thanks.