Enable Modern Authentication for Office 2013 on Windows devices
You may have heard of Modern Authentication, modern-auth is likely to replace Basic Auth which has traditionally been the authentication protocol of choice for technologies such as Microsoft exchange.
When accessing Exchange Online fro example from a client like Outlook or ActiveSync, clients have traditionally used Basic Authentication (also known as Legacy Authentication). Modern Authentication uses web-based sign via OAuth in allowing full single sign on, and rich multi-factor authentication processes.
Modern-Auth will be much more secure and efficient however anyone still utilising older Office products such as Office 2013 may find that they will experience authentication issues with EoL unless the following steps are taken.
To enable modern authentication for any Windows devices that have Office 2013 installed, you need to set specific registry keys.
Modern authentication is already enabled for Office 2016 clients, you do not need to set registry keys for Office 2016.
To enable modern authentication for any devices running Windows (for example on laptops and tablets), that have Microsoft Office 2013 installed, you need to set the following registry keys. The keys have to be set on each device that you want to enable for modern authentication:
ENABLE MODERN AUTHENTICATION FOR OFFICE 2013 CLIENTS
If you're currently signed-in with any of the client apps, you need to sign out and sign back in for the change to take effect. Otherwise, the MRU and roaming settings will be unavailable until the ADAL identity is established.