Configuring preferences and options in Outlook.com
Indeed it's free - but for those of us who subscribe to MS and base our operations around the MS estate (and therefore pay MS quite a lot of money year on year) it seems very poor that they do not provide a mobile version of outlook on the same basis as the desktop versions. In general I'd certainly pay for it - although of course I would expect some effective support.
I have expressed my disappointment via the app feedback more than once already.
Fingers crossed they'll fix it sometime before 2022.