If you want to use Kerberos authentication with Exchange-RT, you need to first install the Exchange Messaging API (MAPI) before installing the module.
To install the Exchange Messaging API (MAPI):
Because Exchange MAPI cannot be installed on the Outlook machine, you need to uninstall Outlook from the agent machine using the Add or Remove Programs option from the Control Panel.
After uninstalling Outlook, download ExchangeMapiCdo.exe from the Microsoft Download Center.
Follow the installation procedures on the Microsoft Download Center page from step 2.
NOTE:This is not applicable for Exchange Online.