iCloud ics invitations sent to Exchange on iPhone won't sync
One of my users periodically receives iCloud calendar invitations sent to his Exchange account. He used to open the e-mail messages on his iPhone, open the attached ICS file to add it to his Exchange calendar on his iPhone, and then it would sync back to the server and show up in Outlook on his PC. Apparently this stopped working recently, and I was able to verify it using several different iPhones and iCloud accounts.
To replicate the issue, this is what I did:
1. Create an iCloud account using a separate e-mail address.
2. Create a calendar event in iCloud.
3. Send an invitation to my Exchange e-mail address.
4. I will get an e-mail from iCloud on my iPhone and Outlook, with an attached ICS file.
a. If I open the ICS file on my iPhone, I can add it to my calendar. It will then show up ONLY on my iPhone. It never propagates back to the server, so it never shows up in Outlook. (Only my Exchange calendar is enabled on my iPhone. To verify, if I turn off or hide the Exchange calendar on my iPhone, the event disappears.)
b. If I open the ICS file in Outlook and add it to my calendar, then it propagates immediately to the server and shows up immediately on the iPhone.
We are using Exchange 2010 and iOS 9.2.1. Any clues as to where the disconnect may lie?
iPhone 5c, iOS 9.2.1
