This was has been baffling me for a while now. We have successfully migrated over to Exchange 2010 SP1. Currently our users are still using Outlook 2007 to connect to Exchange. When testing Outlook 2010 I have noticed an annoying behaviour in that people who I had previously attached their mailboxes to my Outlook (in 2007), are also now showing up in Outlook 2010.
The annoying this is, this is a clean profile, I have added NO additional user mailboxes, yet these still show up as available within Outlook. I can't navigate to Add / Remove mailboxes, because there is nothing there to remove, yet this phantom mailboxes are still there, and still accessible.
How do I get rid of them? I have to think this is a server side setting on Exchange 2010 / or stored in AD, as this test machine is a clean build with a clean profile.