Update: the change mentioned in this article has been rolled out to all commercial tenants.
Many of you may rely on Exchange Online mobile device access rules to ensure that only approved devices (...
Updated Feb 08, 2021
Version 9.0
Blog Post
4 MIN READ
Upcoming Exchange Online Device Access and Conditional Access changes with Outlook mobile
Hmm, but Microsoft Corp. knows better 😛
WindowsMail is listed in https://outlook.office365.com/ecp/ in Exchange ActiveSync Device Access rules:
"Create rules that allow Outlook on Windows devices for Exchange ActiveSync connectivity (WindowsMail refers to the Mail app included in Windows 10)"
https://docs.microsoft.com/en-us/exchange/clients-and-mobile-in-exchange-online/outlook-for-ios-and-android/secure-outlook-for-ios-and-android#option-1-block-all-email-apps-except-outlook-for-ios-and-android
it looks like Mail app is "forgotten" in all Microsoft documentation, but from admin point of view it is "better" than other email clients - it auto-updates without admin rights in background.
Definitely Mail app needs some love from you guys.