Admittedly low-tech, but you can change their Reply-To <staff@myoffice.com>, set all their outbound to BCC to that account, and set the Delete to 15-30 days old.
Each user has their own account, accountability, and they have a shared queue.
If you are using Updox, you can have the Reply-To go to one of those accounts so that there is a true shared queue.
