After some updates today Microsoft Lync kept on asking me  to sing in. If I canceled the dialog an Exchange server error was displayed:

Error

Lync cannot connect to the Exchange server. To restore this connection, please try signing out and signing back in. Until the connection is restored, history, voice mail and Outlook-related features will be unavailable.

Solution

After the update the system clock was set to the wrong time. Restoring the system time to the correct time and restarting Microsoft Lync en Microsoft Outlook the problem was resolved.