1. Navigate to https://admin.microsoft.com/ and sign-in with your administrator credentials.
2. In the navigation panel on the left, expand the Support section and select New service request
   (If you do not see this option, click "Show all" at the bottom of the panel.)
   
   
   
   
3. On the new panel on the right side, type EWS into the search and choose the "Increase EWS throttling policy" option.
   
   
   
   
4. Click "Run Tests" to determine the current throttling state:
   
   
   
   
5. After the test completes you will be given one of three results, as below:
   
   a) "The Exchange Web Services are Throttled." with an option to request the throttling be temporarily changed. 
   
   
   
   After clicking "Update Settings", a confirmation message will be shown.
   
   
   
   b) "The Exchange Web Services are Throttled." with a note advising to create a new service request with Microsoft Support to change the throttling policy.
   
   
   
   c) "Your Exchange Web Services are not currently throttled." with a note stating when throttling will be reapplied.
   
   

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Further reading: Click here for Further information about EWS throttling

Should need any assistance with the above procedure, kindly reach out to Microsoft support directly.