HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Office\15.0\Outlook HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Office\16.0\Outlook If you are using Office 64 bit, check this registry key and create it if it does not exist. See 64-bit editions of Office 2010 for Microsoft's recommendations. Also, you cannot mix-and-match Office 'bitness' - you need to use all 64-bit or all 32-bit Office applications.
SET OUTLOOK AS DEFAULT MAIL CLIENT WINDOWS 7 64 BIT
There is no benefit in using Office 64 bit for "normal" users. Using 64-bit Office is not recommended unless you need large (2GB) file support in Excel or Access.
Using Outlook 64-bit with 32-bit Applications (In older versions of Office, the option is called Repair.)