We have the same problem with one of out iPhone 5s and Exchange 2010. Out of all our device this is the only one having this issue.
The device is a iPhone 5, recently updated to iOS 8.0.2 from 7
our mail server is an Exchange 2010 server.
Symptoms:
Email app works, email is displayed, but when you open a email to read to receive the message, "This message has not been downloaded from the server."
Browsing the folder structure of the Exchange is not present at all.
in account settings the Automatic Reply displays "Loading..."
On the Exchange server there are no specific event logs to indicate a problem, besides the usual Event ID 1040 "The average of the most recent heartbeat intervals [538] for request [Sync] used by clients is less than or equal to [540]."
What we have tried:
If you remove the account and add it back in it works fine for about a day, then it falls back to the above problems.
We have done this everyday for a week now.
Changed most of the settings in account setup to no success.
Restarted the phone every step of the way.
Removed the ActiveSync record in Exchange for the user account and let it recreate upon connection again.
Nothing has worked yet.
Again this is one iPhone 5 with this problem in a list of devices ranging from iPhones including 4, 4S, 5, 5S, 6, and iPad.
If we have any breakthroughs, I'll post.
Just wanted to document the problem.