I was intrigued by this thread so I gave it a test from my Xiaomi MI 10 device.
1. Installed outlook
2. Entered my e-mail address when prompted
3. It showed a screen where I could choose the type of server (Office 365, Exchange, IMAP, POP, etc). I choose exchange.
4. Entered my password
5. Setup done.
The account seems to work and use EAS as I was able to check in connectivity for my test user.
- For the domain i have IMAP, SMTP, EAS, EWS, MAPI autodiscover enabled.
- The user has EAS/MAPI/EWS enabled.
- In the test domain DNS I have:
* A SRV entry for autodiscover that points to the main DNS name of our server
* An autodiscover.domainname.tld entry that points to a website with valid SSL certificate that redirects /autodiscover/autodiscover.xml to our.smartermail.server/autodiscover/autodiscover.xml
* Also a redirect of domainname.tld/autodiscover/autodiscover.xml to our.smartermail.server/autodiscover/autodiscover.xml (this last one seems very important and avoir a lot of trouble with autodiscover as it is the first url checked by AD).
If it can be of help....
ps: Outlook version