Outlook account not syncing on iPhone

I have an outlook email account that started going wonky after the latest s/w update. Multiple emails show unread even though I have read them while using my Mac desktop. When I view 'all inboxes' and select filter for unread emails, none show up even though they show unread while viewing 'all inboxes'.

I've deleted/reconnected the email account on iPhone, I've reset network settings, and I have confirmed that the emails do show 'read' when logging into outlook via browser.

So what's a man to do?