I am currently using Office 365 through Cloudflares’ NS records. The MX record for my account at Office 365 points the protection.outlook.com.
The issue is that because our MX record points of outlook.com, all the other users in our domain cannot access their email.
We have tried to set up a connector in Office 365 Admin panel, and although the tests show successful, no email is received. We are caught between our host insisting we change the NS records away from Cloudflare, and Microsoft telling us that it it impossible to have some users on Office 365, and others on our hosted domain.
I have trouble believing that this is a situation unique to myself, and there is no alternative solution.