outlook contacts synchronized over network

[webitect]

Hello

I have one user "Joe" whose Outlook contacts has everyone else's contacts as well. For example, when I add a contact in my laptops Outlook, then bring the laptop to work and connect to the network, that new contact gets synchronized into Joe's outlook. None of my other Outlook users experienced this. Only Joe's. How can I fix this? I tried looking into the settings of my Outlook but cannot find anything
Any help will be greatly appreciated. Thanks

Ray