Contacts from CRM being sent to Outlook without Outlook for CRM

We upgraded our customer from Dynamics CRM 2011 to 2013 on premise.  They do not have the CRM Outlook client installed.  Their users Outlook is being flooded with multiple and duplicate contacts from CRM.  We are using server side sync but since they are not using the Outlook client we do not have the options to turn off Contact syncing or even change it to only be one way --Outlook to CRM.  Recommendations on how to fix?