in ZCS free/busy is real-time. as soon as any change is made in a mailbox, that change will be reflected in any UI that show's free/busy. ZCO configures Outlooks internet free/busy client which sends requests in real-time to ZCS and renders the real-time free/busy status of attendee's.
I tried the steps you mentioned below and am not seeing any discrepancies across ZWC and ZCO wrt free/busy lookup. |