Managing personal Outlook.com account settings, security, and privacy
Hello, how are you, thanks for posting your concerns in the microsoft community, the message if the web address is legitimate: http://login.microsoftonline.com is generally used by applications such as the Windows Azure Active Directory synchronization tool (to synchronize with Microsoft's online Azure AD service) to authenticate against those services. I can give you more information of Active Directory and likewise you will assure yourself or inform you about what they are asking you
https://docs.microsoft.com/en-us/azure/active-d...
Best Regards
Miguel C.