EWS is giving HTTP Status 500's for specific users
Scenario: You have a user complaining that they cannot access mail through Outlook 2011. When you search the Exchange servers IIS logs, you see a bunch of HTTP 500 responses provided by the Exchange server only for that user. You also found out that this user is on travel.
Resolution: Instead of changing the timezone to reflect the area the user was in, the user adjusted the current time. Changing the timezone to where they were at or adjusting the time back to the current time of the original time zone resolved this issue.
Resolution: Instead of changing the timezone to reflect the area the user was in, the user adjusted the current time. Changing the timezone to where they were at or adjusting the time back to the current time of the original time zone resolved this issue.