Same issue.
There are 2 fixes:
Fix 1:
1. Go into Manage Accounts in your mail app and DELETE the Outlook account (the one that is giving you the annoying message).
2. Tap on Add Account and add Exchange (not outlook.com account)
3. It will say something like this does not look like a work or a school account -> Tap on Continue setting up an account (I did not really read and memorize it
)
4. Enter your Outlook.com username and password and it should work!
Fix 2:
1. Set the date manually to 2018 (Settings -> Time & Language -> Date & Time) and save it.
2. Go to your mail app and sync the Outlook account (should be syncing with no issues).
3. Go back and set the time and date to update automatically (or set it yourself to whatever you'd like)
At least it has been working for a few hours for me including Calendar, Contacts, etc.
Hope this helps until they release a proper fix