You may encounter the following issues in Microsoft Lync 2010 or Lync 2013 in a Lync Server 2013 environment.
You cannot send an instant message. Additionally, you receive the following error message:
This message may not have been delivered to xxx because there was no response from the server.
You cannot change your presence status.
These issues occur because the RtcHost.exe process that is running on the Lync Server 2013 front-end server is restarted unexpectedly. This is caused by an issue in the IIMFilter component.
To resolve this issue, install the following cumulative update:
2987510 September 2014 Cumulative Update 5.0.8308.815 for Lync Server 2013 (Front End Server and Edge Server)