Modern authentication brings Active Directory Authentication Library (ADAL)-based sign-in to Office client apps across platforms. It is not turned on by default for Exchange Online. To turn it on, run the Windows PowerShell command in the following procedure.
Turn on modern authentication for Exchange Online
Connect to Exchange Online as shown here.
Run the following command:
Run the following command to verify that change was successful:
Get-OrganizationConfig | ft name, *OAuth*