Recent changes to Office 365 tenants to be FedRAMP-compliant is causing problems for some users with personal and government email accounts in the Outlook apps for Android and iOS.
Microsoft made a change to the government cloud accounts (GCC) to make the FedRAMP compliant and unfortunately, it caused problems for Outlook mobile users, removing their personal account from Outlook or preventing them from adding work email accounts.
Exchange Online administrators can use the following cmdlet to give Outlook for iOS and Android users access to features and services that are not FedRAMP compliant:
Set-OrganizationConfig -OutlookMobileGCCRestrictionsEnabled $false
At any time, access can be revoked by resetting the parameter back to the default value:
To restore the default value and make the features and services FedRAMP compliant, use this cmdlet.
Set-OrganizationConfig -OutlookMobileGCCRestrictionsEnabled $true
Administrators can read more about GCC, the tenant setting, and non-FedRAMP compliant features here :
Using Outlook for iOS and Android in the Government Community Cloud