After some months of use of Outlook APP for IOS, today I have discovered that Outlook has big limitations on the Office 365 account. The support answered me:
"The migration has been done slowly with the time and the limitation was set not so long time ago. It's set to uphold the highest security standards an to make sure that information is kept within it's region. Now you are allowed to use only two accounts from the same region. That is the maximum limit."
I and my colleagues have to check more than 2 accounts, emails, calendars, onedrive files. So we have to change APP... That's abnormal, Microsoft tell us do not use his APP, we have to find other compatible APP with Office 365... I haven't find a page, a FAQ where I know about this limitations. Many many months ago and now from some times Microsoft put a limitation to only 2 account without notify of that their users.