Your on premise exchange server has zero connections to outlook.com. OWA (Outlook Web Access) looks similar to outlook.com but has otherwise nothing to do with it.

Then let’s call outlook.office.com, and that’s an OWA, and you’re redirected there if you login on outlook.com. And that’s the exception when on prem Exchange servers really work as more than mere proxies nowadays. I’m quite sure that there are still real fully on prem solutions, but it’s laughable these opinions, that most company really care about this. They simply don’t.