Our office uses exchange 2010 and I have a strange issue. I built a new computer for a new hire that replaced one that left. The user gets phantom access to the previous employees e-mail and mailbox. The only coincidence is that the new hire is at the old hire's desk.

New computers, not even the same ones used by the previous employee.
Names are not even close to similar.
User names are not even close to similar.
No mail forwarding or permissions to access the previous employees account are on the new hires profile.
Absolutely nothing was transferred or copied from the previous employees machines to the new hire PC.
The accounts were disabled/activated on different dates.

Does anyone have any idea of what would cause this or what I can read up on related to this as it's a severe security risk in general with other accounts.