Consider the following scenario:
User A schedules a Microsoft Lync 2010 conference by using Outlook, and then user A invites user B to the conference.
The Simple Mail Transfer Protocol (SMTP) address of user A contains both uppercase and lowercase letters.
The SMTP address of user B contains only lowercase letters.
User A and user B both have the update installed that is mentioned in Microsoft Knowledge Base (KB) article 2496325.
In this scenario, the Presence calendar data of user A is not changed to In a meeting successfully during the conference.
This issue occurs because of an error when the calendar capability of the user A is processed. The error is caused by a case-sensitive comparison of the SMTP address.
To resolve this issue, install the following cumulative update:
2571543 Description of the cumulative update package for Lync 2010: July 2011