iphone 6 with iOS 8.1 using MS 365 exchange "read" emails remain unread in outlook or OWA
We use MS 365 exchange online for company email and we have our mailboxes sync with our iPhones. Recently employees have upgraded their older iPhones to the 6 or 6 plus with iOS8.1 or higher. Since upgrade multiple users are reporting that any emails marked "read" on their devices will not update as "read" in outlook for windows or Mac and also OWA. This then causes the user to have to manually mark the emails as "read" in outlook or OWA and is very frustrating and time consuming.
Side note: new emails arrives in all 3 locations (iPhone, OWA, and outlook), so no emails are missing.
Troubleshooting steps taken.
1. Manually forcing the device to update the exchange mailbox by pressing refresh.
2. Turning off all data (cell data and wifi)
3. Removed the exchange account from the device and added it back.
4. Reset network settings to factory.
5. Marked email as "read" from OWA or outlook, iPhone do not update still says "unread"
6. Loaded mailbox onto an iPhone 5s and iPhone 4s and unread emails marked as "read" updated as "read" in all 3 locations (iPhone, OWA, and outlook)
7. Disabled and enabled ActiveSync of the affected users mailbox from the admin console in MS 365 exchange online.
7. Called MS 365 exchange support and they didn't see anything in the logs recorded from the iPhone 6.
Any help, suggestions or to even know that others are experiencing this same issue would be appreciated.
iPhone 6, iOS 8.1