Refer to the options under Tools, Send/Receive, Send/Receive Settings,
Define Send/Receive Groups. By default there is one group listed - if you
edit this you can unselect the folders you don't want synchronised.
Synchronisation occurs when saving an offline copy of an Exchange mailbox or
a Remote Mail setup. Do you have any of these? Do you have any more
information as to where the folders are being synchronised to?