It used to be eas.outlook.com but that doesn't seem to work anymore. The docs online (https://support.microsoft.com/en-us/office/set-up-email-in-android-email-app-71147974-7aca-491b-978a-ab15e360434c) still say that it is, but that endpoint just returns a 401 Unauthorized for around 19 out of 20 requests (and will inexplicably goes through seemingly randomly).
I'm trying to set up my Outlook.com account to work with a third party email app. If I just spam "retry" when it says unauthorized, after a few dozen retries, it magically works. If I remove the account and try to add it again, the same dance occurs. I've tested two separate third-party email apps and also tried setting up the account in Desktop Outlook as a manual Exchange account, and similar behavior is visible in all.