A Throttling Policy for EWSMaxSubscriptions could be defined and applied to the organization with a value of zero. This will prevent the Exchange server from sending EWS notifications, and prevent client applications which rely on notifications from functioning normally. Examples of impacted applications include Outlook for Mac, Skype for Business, notification reliant LOB applications, and some iOS native mail clients. If you determine that your system is at high risk then you should evaluate the proposed workaround. A planned update is in development.”]
Source: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2020-17052