I have an O365 domain (contoso.org). I have a separate Google domain (northwind.org). Currently I sync users/passwords from O365 to Google and the authentication is handled byAADand Google respectively.
Now I want to integrate my Google auth intoAADand letAADhandle the login - but I want to keep my Google users in their northwind.org domain.
Is this possible? I know I can haveAADhandle Google authentication. What Idon't know is can I have 2 separate domains in my O365 tenant - onefor O365 users and one for Google users.
I don't think so, the recently introduced Google federation feature should cover the auth process but that's pretty much limited to Azure AD - none of the Office 365 services will "know" how to handle such users. Though in all fairness, you can actually create mailboxes for @outlook.com users now in O365 (requires some tinkering) or give them Admin rights, I simply haven't bothered to check the Google scenario :)
If I understood correctly, you want to authenticate against AAD and keep your existing Google and O365 emails? I haven't tried that but sure, it is a supported scenario. You do need to register (and verify) both domains to AAD, configure Google SSO to use AAD, and add Google App to AAD.
If you are looking for a scenario, where your emails are in Office 365 and you want your users to be able to login with their Google account, that is also supported scenario (and tested by me.) A bit more tricky to setup but doable. Let me know if you'd like know more about this.