Forum Discussion
Solved
Exchange Activesync and iOS 12.3.1
Our goal: Allow users with personally owned iOS devices to be able to use both Outlook for iOS and the native mail app to access work email. iOS devices are required to be at iOS version 12.0 at l...
EmyLoanzon
you need to separate mail protocol and auth methods.
EAS/REST are protocols to get mails and EAS is used by native iOS mail client, REST used by Outlook for iOS.
Legacy/Modern auth is a way to authenticate in services, but it doesn't affect way of getting messages.
iOS 11 started to support Oauth 2.0 (modern auth) but it still uses EAS to get your messages.
So, for now there is no way to let users use native mail client without using EAS.
If you really need to have native mail client, i would recommend to use Conditional Access policy to block legacy auth, so everyone will be using modern auth even if native mail client.
EmyLoanzon Correct, iOS 11 or higher supports Modern Auth. However, I believe Exchange Online email is still delivered to the native Mail app using EAS vs REST with the Outlook mobile app.