Lync Online supports presence interoperability with an on-premises deployment of Microsoft Exchange Server 2007 and Exchange Server 2010. The Lync Online service provides presence updates based on calendar information and Out of Office details that appear in Lync 2010 (see Lync Online Service Description for more). The presence information in Outlook is provided via the Lync Client and Lync relies on Exchange Web Services (EWS) and Exchange Autodiscover service to retrieve information for Availability, for Free/Busy, for Out of Office, and for Contact Search.
When all of the following conditions are true ...
... the Lync Online user object in the Office 365 directory won’t have an SMTP address stamped. With no SMTP address available, the Lync Client can't query the on-premises Autodiscover and EWS endpoints to retrieve Free/Busy and Out of Office info. In this situation you must either