munybuny :
basroil :
Contacts you can't delete are contacts your client does not have authorization to delete. Figure out what service those contacts belong to and delete them from the service.
I am not sure I understand what you mean. What Service are you meaning. My ISP? All my contacts are resident within the Windows essentials Mail program resident on my computer. Sorry for not understanding.
1) There is no Windows Essentials Mail that comes with Windows 10. The mail app in 8 and 10 is entirely different. If you have Windows Essentials downloaded and installed, you may need to reinstall it.
2) Services = mail providers, like outlook.com/hotmail.com/yahoo.com email providers.