Personal Information Store
There are two ways you can work with Office 365: locally or with a Server.

The desktop version of Microsoft Outlook saves the data (Inbox, Calendar, Contacts and Tasks) in a Personal Information Store (PST) The PST file is saved locally. With Microsoft Office 365, you can work with a Microsoft Exchange Server. Servers are programmable!

4. Try It: Review the Personal Information
We are using Microsoft Exchange. Lync will use this Calendar to update your presence.

And Try This: Update Your Presence
Lync also uses your Contacts to determine how much information is displayed. The Contacts can be identified as Workgroup, Friends and Family, and Colleagues.

Save, Save, Save! These Save options keep a copy in the Microsoft Outlook folders.
Instant messages (E-mail folder)
Call logs (E-mail folder)
Lync Contacts (Personal Contacts folder)

Keep going...

Microsoft Lync 2010->Options->Tools->Options->Personal