ErrorTooManyRequests - how to fix?
Description of the error code "ErrorTooManyRequests"
Domain: Exchange
Code: ErrorTooManyRequests
Type: Temporary error (Please try again later. If multiple temporary errors occur, contact support.)
Description: Exchange received too many requests.
Possible solution: The EWSMaxConcurrency parameter might be set too low.
This issue might be solved by assigning ApplicationImpersonation to the integrating account, which will allow it to operate with a copy of the resource budget of the resource it is accessing.