When you receive that message, it means there is something wrong with the network itself. This could be caused by the lack of an Internet connection or the firewall/Internet security applications installed on your PC. Firstly, check the proxy in the Internet Options > Connections > LAN. You can access it using Windows + R > inetcpl.cpl.
Secondly, start your Firewall/Internet security app and add the Outlook to the Exceptions list.
Reboot the PC and then make sure that the account is properly configured in Outlook.