Microsoft Outlook shares your data with 801 third parties to:

— Store and/or access information on the user’s device

— Develop and improve products

— Personalize ads and content

— Measure ads and content

— Derive audience insights

— Obtain precise geolocation data

— Identify users through device scanning

Although Microsoft explains that it is possible to switch back to the previous apps at any time, the data will already be stored by the company. This allows Microsoft to read your email.

https://proton.me/blog/outlook-is-microsofts-new-data-collection-service