Office 365 Unified API authentication request doesn't redirect to login (vs. Azure AD that does)

Question

I just replaced my app OAUTH2 authentication from Azure AD to Office 365 Unified API (i.e., switched from login.windows.net to login.microsoftonline.com). Problem is that login.microsoftonline.com returns 200 to the authentication request, instead of 302 (redirect) that the login.windows.net does (which is what should be returned by the unified API as well - see respective documentation on MSDN.

Here is an example - Office 365 Unfied API vs. Azure AD. Both get you to the Microsoft login page but only Azure AD redirects you there (i.e., returns 302).

What am I missing?

Answer 1

login.microsoftonline.com is not exclusively used for Office 365 unified API. This is an update the AAD team did for all flows a few months back:

http://blogs.technet.com/b/ad/archive/2015/03/06/simplifying-our-azure-ad-authentication-flows.aspx