In the Change Account dialog box for an existing account in Microsoft Outlook 2013 or Outlook 2010, the Check Name command is unavailable (appears dimmed).
This behavior is by design. By default, Outlook connects with Microsoft Exchange Server through the AutoDiscover feature. After the connection is successful, the edit boxes and the Check Name command are disabled to prevent future modifications.
Article ID: 3062350 - Last Review: 15 May 2015 - Revision: 1