emails keep showing back up on BB with exchange 2007

[carboncow]

I am very much NOT a BB admin but I am the admin of our small business network. Never had an issue with IMAP and my BB user here but we just switched to a Exchange 2007 environment.

Facts:

1. When user choses to delete on handheld & inbox it works as expected. Email disappears everywhere.

2. When he selects "handheld only" it appears to be gone but once he opens his Outlook Client (also 2007) it pulls it from the Exchange Server (2007) and then shows backup on his BB as unread.

Can you point me in the right direction, my search techniques didn't work so well and I'm sure this is a very common concern.