As we discuss in outlook calendar issue posted by @languageservicesco, the implementation of AirSync in eM does not work correctly and the support team doesn’t recognise it. They keep saying that all works fine.
If you don’t care about calendar/contacts, set up the account using automatic setup and then disable AirSync. Just yesterday, I found out that it works this way.
Of course, you lose access to people/notes/calendar, etc as the setup relies comletely on IMAP.