Microsoft already has an Outlook mobile app for Android. But it seemingly is gearing up to release a new one that's known as "Outlook Lite," according to its own Microsoft 365 Roadmap.
The mention of the coming Outlook Lite app for Android was added to the roadmap on June 30. According to the entry, Microsoft plans to make the new app generally available worldwide in July 2022. The brief description of Outlook Lite says: "An Android app that brings the main benefits of Outlook in a smaller app size with fast performance for low-end devices on any network."
The new roadmap entry perhaps could be referencing an updated version of this app or a more broadly available version of it. I've asked Microsoft about the new Outlook Lite roadmap entry but have not received any word back so far. Update (July 5): A spokesperson said Microsoft has nothing to share beyond what's on the roadmap at this time.
Microsoft currently is testing publicly its new "One Outlook" client for Windows. One Outlook/Project Monarch, which looks and feels a lot like Outlook for the Web/Outlook.com, was said to be designed to unify the Windows, Web and Mac codebases for Outlook. Earlier this year, Microsoft officials said the new Outlook for Windows was meant to bring consistency to the Windows and Web codebases and didn't mention the Mac.