Your Outlook client is reporting that it is not connected to Exchange Server, or is working offline.
Although this problem could have many causes related to incorrect Exchange account settings, make sure that the "Work Offline" menu icon on the Send/Receive tab is not active (highlighted). If this icon is active, click on it to deactivate it. You may then be asked to provide your logon credentials in order for Outlook to reconnect to your Exchange Server.
Applies to Outlook 2010.