Microsoft Lync 2010 cannot publish the Presence calendar data of a user when the Simple Mail Transfer Protocol (SMTP) address of the user contains uppercase letters.
This issue occurs because of an error when the calendar capability of the user is processed. The error is caused by case-sensitive comparison of the SMTP address.
To resolve this issue, install the following cumulative update:
2496325 Description of the cumulative update package for Lync 2010: April 2011
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.