Corporate environment. Outlook 2010 running on Windows 7 32bit. iOS 8.1.2 running on iPhone 6.
User 1 sets up a meeting, using Outlook 2010, and sends the invite to User 2. User 2 gets the meeting notification in Outlook 2010 but not on the iPhone.
Also, if User 2 creates a new meeting on their iPhone the meeting never shows on User 2's Outlook 2010 calendar.
The iPhone is using Mobile Iron to handle the Exchange account.