Microsoft today posted the below steps for developers who are interested in bringing their add-ins to Outlook for mobile.
- Add-ins that support mobile must pass a strict set of validation criteria, so we encourage you to share your scenario ideas and mockups for pre-approval before you start implementation, using the form at https://aka.ms/outlookmobileaddin.
- Decide what scenarios to enable on mobile. Not every action makes sense on the small screen, so be sure you’re highlighting the most important functionality of your add-in for mobile. Keep in mind that only mail read scenarios are supported right now.
- Update your manifest to declare support for the Mobile Form Factor and define the actions you came up with in step 1.
- If applicable, make sure any backend calls to the mailbox are using our REST API. EWS requests are not supported on mobile.
- Build mobile-specific UI for the small screen using our design guidelines.
- Submit your add-in to the Office Store for validation. You can find instructions here.
Add-ins support is also coming to Outlook for Android soon. Learn more about it here.