I have a team of sales people. I add each of them to the 'sales' group.
I set up some IMAP public folders, say 'incoming', 'pending' and 'finalised' and give the group appropriate permissions.
When a new staff member joins the sales team, or someone leaves, I merely update the 'sales' group with the modified members. The alternative would be to go through each of the public folders and set explicit permissions for each new person and remove old permissions.