For those behind MDM profiles, I found a small workaround that would give you read-only access to your outlook calendars to show in the iOS Calendar and therefor show up in Agenda.
Read-only calendar in iPhone/iPad native Calendar app:
- Open Outlook from your web browser (not desktop app or mobile app).
- Go to Settings > View All Outlook Settings > Calendars > Shared Calendars > Publish a Calendar > choose your calendar and it will give you an .ics link
- On your iPhone/iPad, go to Settings > Calendar > Accounts > Add Account > Other > Add Subscribed Calendar > paste the .ics link.
Note, this is viewing only, you will not be able to create or edit Outlook appointments, but you can view them and get notifications from them. As Outlook calendar is my main calendar, the inconvenience of not being able to create an event is small compared to not being able to use the app at all.