Deploying new features to a massive 100-million plus user community takes a lot of planning and careful management. Outlook Mobile caters for both consumer and commercial users, and different methods are used to deliver new features to the two groups. Sometimes this means that different users in the same tenant can’t access a new feature even if they have the right software.
https://office365itpros.com/2019/08/30/how-microsoft-deploys-new-outlook-mobile-features/
