The article describes the issues you might experience if you are using Office Communicator 2007 IM client with Lync 2010 server.
- Office Communicator 2007 R2 client won't connect and displays an error like below:
- The IM and call history are not stored in the default Exchange mailbox correctly when you use Office Communicator 2007 R2.
All the above issues can be fixed by upgrading the Office Communicator 2007 R2 to Microsoft Lync 2010 or by downloading a hotfix from Microsoft.
Read the Knowledge Base article on Getting Started With Lync 2010/2013 For Windows to install Microsoft Lync 2010.