Azure AD user logging into Outlook client on a mobile device fails with error 50158
Error 50158 - External security challenge was not satisfied
End-users should log into Outlook.com to complete the setup of their profile and confirm their Office 365 account is working properly. When this is complete, logging into the Outlook mobile client should be successful.
Note: Microsoft Azure AD Conditional Access protects cloud applications only when the user access originates from the following client applications:
Conditional Access currently cannot enforce access controls in older Office clients, such as Office 2010.