Using Outlook for Android in business environments for email and scheduling
I contacted Outlook Mobile Support via the app help portal (very timely support, by the way). Here is the reply on this issue. If more people contact them they will elevate it to the proper team to make changes.
"Thank you for contacting the Outlook Mobile Support. We'll be happy to help.
We were just informed that this is a new feature/update that was being rolled out in the Outlook App. As of now, there is no way to turn it off or disable it but we'll definitely pass along any feedback you have to our Engineering Team. For now, users can go to the menu located at the bottom of the screen and choose, "open in browser" so for you to see the option that was previously used.
We appreciate your continuous support and feel free to contact us again for any other inquiries about the Outlook App.
Friendly Tips:
-> Keep your App updated by checking your Google Play Store and be sure that you're getting the best out of the App.
-> Save at least 1GB of memory for the App for the best performance.
-> Have Fun and stay positive."