I had an issue where Outlook 2007 and above, with an Exchange 2010 server, would constantly ask for a password. It was a problem with AutoDiscovery authentication. The solution was found here: Open a command prompt Type: cd c:\windows\system32\inetsrv\ Type: appcmd list config /section:windowsAuthentication  You’ll see something like this: <system.webServer> <security> <authentication> <windowsAuthentication enabled=”true” useKernelMode=”false”> <providers> <add value=”Negotiate” […]