What devices are using my microsoft account?
How do i know what devices are able to log into and use my id and account
iPhone 12 Pro Max, iOS 15
With a Microsoft 365 account you’d need to login to that account in a web browser with your MS Login ID and see which devices you’ve installed your 5 allowed Office installs on there. It will not show mobile devices using the free mobile Office apps with your MS 365 account though. MS only tracks laptops and desktops (Windows or MacOS machines) that you’ve installed Office on.
There is no way through Apple nor an Apple device to see which devices are signed into your MS account and using your 365 account. Presumably anyone who knows your MS 365 login ID and password could be using your MS account for 365 apps on their Apple mobile devices.