Unread Emails in Outlook 2010 Clients shows both UNREAD AND READ emails when connected to Exchange 2013 Server SP1

We recently upgraded to Exchange 2013 SP1 with a client user-base of Office 2010 Professional Plus / Outlook 2010 SP3.

All Unread Email favorites folders show both Unread and Read emails, just like the inbox. Removal of the folder and recreating yields the same results, as does creating a custom folder. However, in Outlook 2013 there is no problem. 

Is there a patch or hot fix for this issue? Or does anyone know how to fix this issue so that the UNREAD EMAILS SHOW UP IN THE UNREAD FOLDER AND NOT INCLUDE THE READ EMAILS? 

Thank you!

Kim Parker-Polito / Newhall Land